Descartes on the
Heartbeat: The Leuven
Affair

Lucian Petrescu
Ghent University

This paper presents the reactions to Descartes’ account of the heartbeat
expressed by the Leuven professors Fortunatus Plempius and Libertus
Fromondus, reactions that also involved the Utrecht professor Henricus
Regius. I show that the letters exchanged between Descartes and the two
Leuven professors in 1637–1638 stirred a continuous debate, followed
through a series of publications, up to the condemnations of Cartesianism in
1662–1663. I investigate the extent to which the reception of Descartes’ ac-
count of the heartbeat contributed to the initial rejection of Cartesianism in
Leuven and how physiological arguments were motivated by theological con-
cerns throughout these exchanges.

1. Einführung
There is an interesting historical detour in the dissemination of one of the
seventeenth century’s most praised discoveries: the reception of Harvey’s
account of the circulation of the blood is closely intertwined, especially in
the Low Countries, with Descartes’ account of the origin of the heartbeat.
Descartes was one of the ªrst ªgures to support the circulation of the
blood and to give credit to Harvey for it, although he presumably arrived
at the same conclusion independently through his own anatomical experi-
gen. He did so while vocally rejecting Harvey’s views on the muscular
nature of the heart and his explanation of cardiac motion, to promote
his own mechanistic solutions instead. Although Descartes’ mechanical
physiology had been generally well received, particularly in the Northern

I owe thanks to Maarten Van Dyck, Sven Dupré, Charles T. Wolfe, and anonymous review-
ers for comments, to Barnaby Hutchins for having corrected my English, and to Thomas
Gariepy for having kindly provided me with a copy of his dissertation. Research for this ar-
ticle was ªnanced by the Fonds Wetenschappelijk Onderzoek Vlaanderen (FWO).

Perspektiven auf die Wissenschaft 2013, Bd. 21, NEIN. 4
©2013 by The Massachusetts Institute of Technology

doi:10.1162/POSC_a_00110

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Descartes on the Heartbeat

Niederlande, and had quickly become a vehicle for Harvey’s account of the
circulation, this reception was not at all linear; it also generated contro-
versy among the more theologically minded physicians.1 I present here a
sustained exchange over Descartes’ account of the heartbeat that had its
epicenter in Leuven and that, I argue, is not disconnected from the events
that led up to a famous series of condemnations of Cartesianism in 1662–
1663. The events leading up to these condemnations are more complex
and had multiple motivations, but I hope that the re-examination of the
controversy generated by Descartes’ account of the heartbeat will shed
more light on the extent to which his physiology contributed to the initial
reception (and rejection) of Cartesianism in the Southern Netherlands.

The history of the propagation of Harvey’s medical discovery and its
connection to Descartes has been explored in a number of works. Recep-
tion studies tell us how conservative or progressive these physiological
ideas were on one side of the English Channel or the other. The greater
success of Descartes’ mechanism of the heart, as compared to Harvey’s ac-
zählen, has been reported to parallel the success of mechanism vs. vitalism,
with the complexities that this entails.2 More recently, Marjorie Grene has
suggested that Descartes’ account of the heartbeat amounts to “a conser-
vative innovation,” when compared to Harvey’s. Das ist, “his position
proved more acceptable also because, in its medical details, it was more
conservative.”3 This is one side of the story; Descartes’ physiological infor-
mation and his scientiªc results may have been more traditional. But the
philosophy behind it certainly was not, and perhaps this weighed more for
his readers. It is true that Descartes retains a number of “conservative”
facts in his study of the heart, and most strikingly the Galenic thesis of the

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1. Scholars tend to acknowledge that Descartes’ account of the motion of the heart was
more successful than that of Harvey. Fuchs (2001), P. 2: “Harvey’s discovery, sowie
Harvey himself, was and is seen chieºy from a perspective that was determined to a great
extent not by him, but by Descartes.” French (1989), P. 47: “The doctrine of the circula-
tion of the blood had its greatest impact in the Low Countries in conjunction with Carte-
sian mechanism.” Grene (2005), P. 93: “as the idea of the circulation came to be accepted,
it was in fact Descartes’ view of the heart’s motion that was, in many cases, accepted as the
more persuasive account.”

2. See Fuchs (2001). Fuchs speaks of “the vital aspect of the circulation” (Part C,
“Harvey”) and of “the mechanical aspect of the circulation” (Part D, “Descartes and his fol-
lowers”). The classic study of Étienne Gilson (1930) is the ªrst to have explored the issue
in depth. Weil (1957) contains a useful list of early works referencing Harvey’s De Motu.
For more recent studies, see French (1989, 1999); Grene (1993, 2005); Gorham (1994);
Anstey (2000); Aucante, “Appendice 6” in Descartes (2000). For recent studies on Des-
cartes’ physiology in general, see Bitbol-Héspèries (1990) and Aucante (2006).

3. Preface to Fuchs (2001) xiii, a thesis developed in Grene (2005).

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Perspektiven auf die Wissenschaft

399

simultaneity of the systole and the diastole in the heart and the arteries.
Jedoch, Descartes’ mechanical explanations and the conceptualization
of the “ªre without light,” which is the core of the Cartesian account,
appeared to be unheard of: “nova est ac inaudita, et prorsus absurda
[opinio],” cried a scandalized reader.4

My revision of the Leuven affair concentrates on the philosophical is-
sues that determined the reception of the Cartesian account of cardiac mo-
tion. It supports the view that Descartes’ account of the heartbeat, gegeben
the philosophical and theological implications of its medical details, War
to a great extent contrary to the medical tradition established in the uni-
Vielseitigkeit; that this tradition reacted strongly against it, largely on theologi-
cal grounds; and that the same medical establishment preferred Harvey’s
physiology as the more conservative one, against Descartes. The circula-
tion of the blood is in itself metaphysically neutral; it can be taken to
appeal both to an Aristotelian and an anti-Aristotelian.5 Descartes’ expla-
nation of cardiac motion is not. The Leuven reception will show that Des-
cartes’ account of the heartbeat was read and discussed not simply as a
medical explanation, but as committing one to particular Cartesian theses
on the nature and functioning of the soul, even before Descartes developed
these theses in his later works, like the Meditations or the Passions of the
Soul.

I start by brieºy recalling the physiological matter at hand in Harvey
and Descartes, and then explore the ªrst reactions to Descartes’ physiology
of the heart from 1637–1644. Dabei, I follow a debate on the heart-
beat between Descartes, Plempius and Regius, and I analyze it as moti-
vated by commitments over the nature of the soul. In the third part I look
at the theological reactions stirred by Descartes’ account of the heartbeat
from Fromondus and follow the development of Plempius’ campaign
against Cartesianism up to the 1662–1663 condemnations. Monchamp’s
Histoire du cartésianisme en Belgique remains an unrivalled source for the
events leading up to the condemnations, which have not been explored ex-
tensively since (Monchamp 1886). Armogathe and Carraud document
the Leuven condemnations of Cartesianism of 1662–1663 through a pre-
sentation of the relevant texts, together with previously unedited ones
(Armogathe and Carraud, 2001). Ariew has brought forward a number of
arguments related to the extension of the universe in the Leuven condem-

4. Riolan (1649), P. 44, inGilson (1930), P. 96.
5. I use “Aristotelian” as a label much in the loose sense that the seventeenth-
century anti-traditionalist rhetoric used it; here it should pick up authors adhering to the
Aristotelian-inspired doctrine of the tripartite function of the soul.

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400

Descartes on the Heartbeat

nations (Ariew 1994 Und 2011, S. 241–267). The texts of 1662–1663
condemn, unter anderem, Descartes’ physiology: the motivations and
context of this historical detail will be explored here.

2. Descartes on the heartbeat
Evidence that Descartes read Harvey’s De Motu appears in his correspon-
dence in late 1632.6 For Harvey, the heart is an empty contracting muscle,
which stirs the blood into motion by its beating and pushes it in and out.7
Descartes’ expressed dissatisfaction with Harvey’s account is that it does
not explain the origin of the beating of the heart, so that we would need a
“pulsiªc faculty” to account for the beating.8 In Descartes’ account, Die
bedrock of the explanation is moved from a pulsiªc faculty of the muscle
to the innate heat within the heart.9 While praising publicly Harvey on
the matter of the circulation itself, Descartes maintained his own explana-
tion of the heartbeat throughout his career, from the Treatise of Man (writ-
ten in 1632), through the Discourse, in his correspondence and until as late

6. Gassendi read Harvey and wrote about it to Mersenne, who then asked Descartes
what he thought of it (AT I 264). Descartes responded in November or December 1632:
“J’ai vu le livre de motu cordis dont vous m’aviez autrefois parlé, et me suis trouvé un peu
différent de son opinion, quoique je ne l’aie vu qu’après avoir achevé d’écrire de cette
matière” (AT I 263). Descartes is taken to have written the Treatise on Man before reading
Harvey. Cf. Descartes to Mersenne, dated 1635–1636: “An non nosti Londini celebrem
quendam medicum nomine Hervæum, qui librum de motu cordis et circulatione sanguinis
conscripsit? quis homo est? Equidem de motu cordis nihil dicit, quod in aliis iam non
extaret, neque illi per omnia assentior; sed quantum ad circulationem sanguinis, trium-
phat, ipsique honor debetur quod fuerit primus inventor, in quo Medicina ei multum
debet” (AT IV 699–700).

7. As a reminder, a central passage: “First of all, the auricle contracts, and in the course
of its contraction throws the blood [. . .] into the ventricle, which being ªlled, the heart
raises itself straightway, makes all its ªbres tense, contracts the ventricles, and performs a
beat, by which beat it immediately sends the blood supplied to it by the auricle into the
arteries.” Harvey (1989), P. 31. For a good comparative account of the two theories of
the heartbeat, see Anstey (2000), S. 421–423.

8. Descartes is explicitly arguing against Harvey on several issues in the account from
the Description du corps humain, AT XI 239–244. Cf. S. 243–244: “Now supposing that
the heart moves in the way that Harvey describes, not only must we imagine some faculty
which causes the movement, the nature of which is much more difªcult to conceive than
what it is invoked to explain: we must also suppose the existence of yet other faculties that
alter the qualities of the blood while it is in the heart.” Trans. by S. Gaukroger in Descartes
(1998), P. 181 (the passage in CSM I 318 is a little obscure; where not speciªed otherwise,
translations are mine.) The “pulsiªc faculty” was familiar from Galen, who used it to ex-
plain the motion of the arteries, as a faculty residing in the arterial walls.

9. For Descartes’ mechanization of the idea of innate heat, see among others Hall

(1970) and Bitbol-Héspèries (1990), S. 67–102.

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401

as the Description of the Human Body (1647) and the Passions of the Soul
(1649).10 One can argue that Descartes’ explanation was better at accom-
modating the corpuscularian physics that was gathering steam in the
1630s and 1640s. From Descartes’ point of view, Harvey’s account poses a
problem of conceivability that can be addressed by Descartes’ physics: Wie
are we to “conceive” a discrete motion of a muscle, as Harvey does, gegeben
that each local motion of a body is accounted for in terms of the communi-
cation of another local motion of a different body? Darüber hinaus, Descartes’
thermogenic account also went along with the established medical knowl-
edge in placing the vital heat within the heart and not in the blood itself
(see Grene 2005 for details on this point). It seemed like the perfect move
for Descartes: to explain new scientiªc facts through his physics while at
the same time keeping the phenomenon in concert with the medical
tradition.

The importance and degree of certainty that Descartes accords to his ac-
count of the heartbeat cannot be overemphasized. Descartes reiterates
every chance he gets, that his explanation of cardiac motion sits at the very
core of his physiological endeavors. “It is so important to know the true
cause of the heart’s movement that without such knowledge it is impossi-
ble to know anything which relates to the theory of medicine. For all the
other functions of the animal are dependent on this,” he states in the De-
scription of the Human Body (AT XI 245 / CSM I 319). In the Discourse of
1637: “Being the ªrst and most widespread movement that we observe in
Tiere, Es [the motion of the heart and blood] will enable us to decide
how we ought to think about all the others.” (AT VI 46–47 / CSM I 134)
The motion of the heart, giving rise to a circular motion of the particles of
the blood, is the paradigm for explaining all bodily motions. Wieder, im
Passions of the Soul, the “continuous heat of our heart” is said to be the “cor-
poreal principle” of all the motions of the body (AT XI 333). And at one
point he speaks about his account in terms of its lying at the heart of his
entire “Plan of a Universal Science”: “I am prepared to admit that if what I
have written on this topic [the cardiac cycle] or on refraction turns out to
be false, then the rest of my philosophy is entirely worthless,” he says to

10. Treatise on Man: AT XI 123–127, Discourse: AT VI 46–55, Description of the Human
Body: AT XI 228–245, Passions of the Soul: AT XI 331–334; Letter to Beverwijk, 5 Juli
1643, AT IV 3–6. A. Georges-Berthier’s thesis (Georges-Berthier 1914), that Descartes
was not too concerned with the origin of the heartbeat in his early writings, has been re-
jected by Aucante in Descartes (2000), P. 245, who points to two early fragments (AT XI
524). Aucante takes the ªrst redaction of the Description to be immediately after the Dis-
course and to continue in 1638, which is consistent with the discussion from 1637–1638
that I am following (Descartes 2000, P. 19).

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Descartes on the Heartbeat

Mersenne in a letter of 1639 (AT II 501 / CSM III 134).11 Descartes’ pro-
nunciations in these passages suggest that the explanation of cardiac mo-
tion is not just one particular physiological account that can be discussed
within the Cartesian system, and accepted or refuted; it is a key piece of
the natural-philosophical project applied to the knowledge of the human
Körper, and in turn validates that natural-philosophical project. That the ex-
planation is closely linked to other fundamental tenets of the Cartesian
program will appear clear to its very ªrst readers.

With this in mind, I turn to the immediate reaction to his account of
the heartbeat, coming from the brieºy inºuential physician Fortunatus
Plempius. The debate with Plempius is followed up through Descartes’
disciple at the time, Henricus Regius and, in parallel, through a brief
exchange with Libertus Fromondus. There are two main letters from
Plempius and Descartes respectively discussing the physiology of the
heart, all in a sustained correspondence of 1637–1638.12

3. Fortunatus Plempius (1601–1671) and Henricus Regius (1598–1679)
According to his own testimony, Plempius met Descartes sometime in the
early 1630’s, while exercising his medical profession in Amsterdam, Und
kept in touch with Descartes through the second half of the 1630’s, Wann
he became professor of medicine at Leuven. In his colorful depiction,
Plempius compared their meeting to that of a Hippocrates meeting a
Democritus.13 At the time, Plempius was already a well-bred and mildly

11. AT VI 46–47 / CSM I 134. ”Projet d’une science universelle” is the projected
title for the book of 1637, as per the letter to Mersenne of March 1636, AT I 339 / CSM III
51.

12. Descartes sent Plempius three copies of the Discourse and Essays, out of which
Plempius sent one to Fromondus and one to the Jesuit François Fournet (AT I 399). A let-
ter from Fromondus to Plempius for Descartes, 13 September 1637 (AT I 402–409) sends
a number of the theologian’s objections on the book (see infra section III). Descartes re-
sponds to Fromondus’ objections through Plempius in the letter of 3 Oktober 1637 (AT I
413–431). Fromondus does not respond, but the discussion continues with Plempius: Des-
cartes adds to Plempius some reºections on Fromondus’ objections in a letter of 20 Decem-
ber 1637 (AT I 475–477) and asks from Plempius his comments on the motion of the
heart. Plempius replies through a letter from January 1638 (AT I 497–499), advancing
brief objections on both the motion of the heart and the circulation of the blood. Descartes
replies at length with a letter from 15 Februar 1638 (AT I 521–534), to which Plempius
replies in March (AT II 52–54) and obtains a second reply from Descartes on 23 Marsch
1638 (AT II 62–69). A reply from Plempius from 20 April 1638 was lost. Descartes thinks
about publishing the exchange (see the letter to Plempius from August 1638, AT II 343–
345), but Plempius backs off, only to publish it himself.

13. Plempius testiªes that he frequented Descartes in Amsterdam in the early 1630,
while Descartes was living in a street of butchers to have easy access to dissection material;
see Plempius (1653), P. 375 and AT I 401. Baillet (1691), Bd. 1, P. 312 writes: “M. Des-

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403

inºuential physician. Born in Amsterdam but educated in Catholic col-
leges and universities (Ghent, Leuven, Padoua, Bologna), he took up a
chair in the faculty of medicine at Leuven in 1633, and he converted to
Catholicism.14 He published his ªrst medical manual, covering the ªrst
year of the medical cursus at Louvain, under the title De Fundamentis
Medicinae libri sex, In 1638 (Leuven: Zegers). The Fundamenta is, im
words of one historian, “one of the most clear and complete works” of
seventeenth-century medicine (Tricot 2000, P. 14). Plempius’ book ap-
peared in 1638, a year after Descartes’ Discourse. He had most likely al-
ready ªnished writing it when he started his correspondence with Des-
cartes, earlier in the same year, but he added part of that exchange in the
published book. We do not have deªnite proof that Descartes knew of
the preparation of Plempius’ book when their correspondence started, Aber
given that he had known Plempius for a number of years before this, Die
odds are that he did. He certainly knew of Plempius’ opposition to
the theory of circulation, for he urged him several times to send him his
objections.15

In the letter to Descartes of January 1638, Plempius brings forward
three experimental objections against the circulation of the blood, all of
which are refuted by Descartes, and four against Descartes’ explanation of
cardiac motion. The second letter, of March 1638, drops the discussion on
the circulation while continuing that on cardiac motion.

Against the circulation of the blood, Plempius objects: that the arterial
blood and the venous blood would have to be the same; that intermittent
fevers, which are caused by localized matter (materia febrilis) in the veins,
should travel along with the blood and cause many fever attacks instead of
just a regular number per day; and that if one ligatures the veins of the leg
of an animal while leaving the arteries free, the leg should swell consider-
ably because of the incoming ºow of blood, which does not happen.16

cartes contait alors Plempius parmi l’un de ses meilleurs amis, et Plempius ne dissimulait à
personne l’honneur et l’avantage qu’il croyait recevoir de cette amitié.”

14. On Plempius, see Tricot (2000); Monchamp (1886), passim; Aucante (1999);
French (1999); Descartes (2003), S. 287–288; Vanagt (2011). CSMK 389 wrongly gives
1661 as the year of Plempius’ death. For a general overview of philosophy at the University
of Leuven during this time, see de Wulf (1908), S. 454–473 and Monchamp, (1886),
S. 3–27.

15. 5 Oktober 1637: “Quæ de motu cordis muginari te scribis avidissime expecto,” AT
ICH 411; 20 Dezember 1637: “Ideoque etiam tuas de motu cordis avide expecto,” AT I 477.
16. AT I 499: “Contra sanguinis circulationem, quam cum Hervæo adstruis, hæc
habeo: 1. Sanguis arteriosus et venosus sic plane similis esset, imo idem, quod repugnat
autopsiæ. Ille ºavior et ºoridior, hic nigricantior et tristior est. 2. Materia febrilis con-
sistens alibi in venulis a corde remotis, quæque adeo febrem intermittentem tantum efªcit,
deberet plures de die accessiones facere, toties scilicet, quoties ªt sanguinis illius et simul

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404

Descartes on the Heartbeat

Descartes’ answers on these matters are arguably convincing. Erste, Er
says, one could object to Harvey that his explanation does not account for
the difference between arterial blood and venous blood, but not to him,
who explains a transformation of the blood in the heart itself. The rarefac-
tion of the blood in the heart makes the arterial blood brighter, and thin-
ner.17 For the second point, Descartes appeals to Fernel and his theory of
intermittent fevers, a good authority to bring in, and dismisses the objec-
tion as a side issue. The ligature experiment, he points out, is precisely one
that shows the circulation, for if one would cut open one of the free arter-
ies, the blood would ºow more forcefully (AT I 531–534).18

Descartes’ answers on the circulation were well received by Plempius:
“As to the others things that you bring forward in favor of the circulation
of the blood, they are sound enough (satis bene se habent), and that opinion
[of the circulation] does not really displease [me].”19 The exchange on the
experimental evidence for the circulation of the blood seemed to end on
Descartes’ terms and Plempius did later become an advocate of Harvey.
But the other matter raised in the correspondence did not have the same
outcome: when it comes to explaining the origin of the motion of the
heart, Plempius was more resilient to Descartes’ arguments. For Descartes,
the two issues—the circulation of the blood and the motion of the heart—
were inseparable; not so for Plempius.

The discussion over the motion of the heart from the two letters (Janu-
ary and March 1638) is considerably lengthier. I will only give a brief
summary. Plempius’ comments are prefaced by a general remark, welches ist
telling for his subsequent points: it is true that Aristotle talks about a cer-
tain heat in the heart, says Plempius, but “our Galenus, contrary to this
opinion, taught that the heart is moved by a certain faculty, and this is
what all we medical men have been teaching up until now.”20 Not only is
he minimizing Descartes’ contribution by reducing it to that of Aristotle,
but also dismisses Aristotle’s position as false according to Galen. In Janu-

humoris febrilis reditus in cor; ponis autem reditum istum ªeri centies, imo ducenties per
diem. 3. In vivo animali ligatis venis plerisque ad crus tendentibus, liberis relictis arteriis,
deberet crus illud brevi temporis spatio mirum in modum tumescere, eo quia sanguis
continenter per arterias inºueret per venas. Atqui tantum abest ut hoc ªat, ut potius, si diu
sinas ligatas venas, pars extenuetur defectu nutrimenti.”

17. This argument is already given in the Discourse, AT I 52.
18. I refer to Grene (1993) for more details on these arguments; here I am more con-

cerned with the discussion on the origin of motion in the heartbeat.

19. AT II 54: “Cætera quæ dicis pro circulatione sanguinis, satis bene se habent, neque

ea sententia valde displicet.” For Aristotle, see De Respiratione, 20, 480A.

20. AT I 497: “Galenus noster contra a facultate aliqua cor moveri docuit, et omnes

hactenus id docemus Medici, a quibus quod adhuc stem hæ faciunt ratiunculæ.”

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Perspektiven auf die Wissenschaft

405

Und, Plempius lays out a Galenist attack on the position that motion must
be generated by a certain faculty, both in the heart and in the arterial
walls. He offers a famous Galenic experiment with ligatures intended to
show that the arteries pulsate in virtue of something ºowing through the
arterial walls, not in virtue of the ºow of the blood through them. Des-
cartes proves the experiment wrong according to “the laws of my mechan-
ics.”21 Next, Plempius questions Descartes’ “mechanics” itself: the process
of fermentation through which Descartes explains the rarefaction of the
blood is a much slower process in nature than what we would need for
the heartbeat. Rarefaction is gradual. Descartes answers to this point at
length and brings in an analogy with certain ºuids, welche, once they have
reached a certain degree of heat, burst out of the pot, very quickly.
He does not go so far as to reproduce experimentally the rarefaction of the
blood though. Wieder, Plempius serves another objection from mechanics:
the communication of motion from the heart to the arteries would not be
transmitted throughout the body instantaneously, which would account
for the simultaneous pulse of the vessels, but only to the neighboring ar-
teries. Descartes refers back to his anti-Galenic experiments for this: Die
blood pushed through the arteries neighboring the heart would in turn
push out the rest of the blood; according to Descartes, the communication
of motion through the body is without loss.

The details of these arguments are important for the experimental
exposition of Descartes’ account, one of the best he ever gave, and they
have been justly exploited by the literature.22 But I would like to call at-
tention to one point detailing the instantaneous rarefaction. According to
Plempius, a heart freshly extracted from a living body continues to beat:
how is this possible for Descartes, if the blood is no longer there to enter-
tain fermentation? Descartes gave several experimental answers to this:
that there always remains some blood, as he had seen in his observation on
ªsh, developed his theory of instantaneous rarefaction and that of the yeast
that remains in the extracted heart to entertain fermentation. The in-
teresting bit however is that Descartes uses Plempius’ own observation
against him, as an argument against the motor force of the sensitive soul:
the soul is in fact not supposed to remain and act in a dead heart.

This objection, he says, seems to me much more damaging to the
view, which is commonly held by others, that the movement of the
heart is due to some faculty of the soul. For how, I ask, can the
movement which occurs in the cut-up bits of the heart depend on

21. The experiment is a common place for early modern Galenists. See Grene (1993),

S. 327–328, for a report on it.

22. See especially Gilson (1930) and Grene (1993).

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406

Descartes on the Heartbeat

the human soul, when it is taken as an article of faith that the ratio-
nal soul is indivisible, and has no sensitive or vegetative soul at-
tached to it? (AT I 523 / CSMK 80–81).

This point marks a shift in the argument from scientiªc (experimental)
evidence to broader concerns. The objection forces Plempius to reply, In
his second letter, that even if the soul goes away, its “power,” some of the
soul’s faculty or “instrument,” lingers:

I think nevertheless that one can save the common opinion [of the
faculties of the soul]: even though the soul in a human heart ex-
tracted from a living body is no more, and consequently neither the
faculty, there remains however for a certain time the instrument of
the soul, i.e. the spirit which acts in virtue of the soul. Thus I re-
tain that in the corpse of a freshly beheaded man contractions, di-
gestions and assimilation of food take place, just as in a living man,
for as long as the heat and the vivifying spirit remain in it.23

The separation between the motor function or instrument of the soul and
the soul itself plays right into Descartes’ hand. Ontologically, this entails
that a quality or power of a substance remains while the substance is gone.
Descartes’ reply is unforgiving, in a change of tone uncharacteristic for
what was until now a courteous exchange:

In order to explain how a human heart cut from a corpse can move
when the soul is no longer present, you resort to the idea that heat
and vital spirits cause the movement by operating as instruments of
the soul. Now is this not resorting to desperate measures? For if
these instruments should sometimes sufªce on their own to bring
about this effect, why not always? And why should you imagine
that when the soul is absent, these effects should occur through
some power of the soul, when you think that no such power is
needed to bring them about when the soul is present? (AT II 65 /
CSMK 94).

In a rare moment of open attack on Aristotelianism, Descartes compared
Plempius’ objections with that of army captains who want to defend

23. AT II 53: “Nihilominus ego vulgarem opinionem salvam facere mihi posse videor;
nam etsi in corde humano exempto anima non sit, nec consequenter etiam facultas, instru-
mentum tamen animæ illi aliquantisper inest, spiritus scilicet in virtute animæ agens. Sic
existimo in cadavere hominis subito decollati ªeri attractiones et coctiones et assimilatio-
nes alimenti perinde uti in vivente, quandiu calor et spiritus viviªcus cadaveri inest.”

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Perspektiven auf die Wissenschaft

407

themselves with poor ammunition, and ªre everything they have rather
than capitulate.24

letters in his Fundamenta Medicinae

The exchange ended here, although Plempius sent another reply, Jetzt
lost. As mentioned, Plempius quoted and reported arguments from Des-
cartes’
later in the year (1638).
Descartes also entertained the idea of publishing the exchange, but mean-
while these letters circulated widely. Descartes’ physiology, before the
publication of the Passions of the Soul and the Treatise on Man, is known
to the learned world through the Discourse and through the letters to
Plempius.25

The second edition of Plempius’ Fundamenta medicinae, von 1644, marked
Plempius’ conversion to Harveyan circulation. After presenting an interest-
ing story of his troubles with the theory, he admitted bluntly that, although
he did not like this novelty at ªrst, having been trying to refute Harvey’s
“praiseworthy arguments,” he realized that he came to refute himself. And
then he set out to probe them through his own vivisections of dogs, welche
ªnally forced him to admit the circulation of the blood.26 It is a resonant

24. AT II 64–65: “Verum imitari vis egregios illos belli duces, qui cum arcem aliquam,
quæ male munita est, servandam susceperunt, licet obsidentibus resistere se non posse
agnoscant, non tamen ideo protinus ijs se dedunt, sed malunt omnia prius tela consumere,
et extrema quæque experiri: unde ªt, ut sæpe, dum vincuntur, plus gloriæ quam ipsi
victores reportent.” Descartes was receiving at the same time the same line of argument
from Fromondus, see infra; this may have prompted this rebuttal, and the use of the plural
can be read as addressing to both Fromondus and Plempius.

25. Years later, In 1643, a Dutch physician, Johan van Beverwijck (Beverovicius, 1594–
1647), shows an interest in this exchange and asks from Descartes his letter to Plempius
regarding the circulation of the blood, alluring Descartes with the intention of publishing
it in a Recueil of letters of “important men.” Descartes sends him the entire dossier: the two
letters from Plempius and his response letter together with the minutes he had taken of
their encounter. Van Beverwijck indeed publishes them in his edition of Epistolicæ Quæs-
tiones (1644; translation in Post 1979). Later on, Princess Elisabeth of Bohemia shows
knowledge of the exchange in her letter to Descartes of May 24, 1645 (AT IV 210). Harvey
himself recognizes the importance of Descartes’ version of the circulation in his second let-
ter to Jean Riolan of 1649, and the English edition of the De Motu Cordis cites, in De
Back’s appendix, Descartes’ experiment of the vivisected beating heart of the eel from his
correspondence with Plempius: Harvey (1653) P. 118. Cf. AT I 508, 515, and pp. 651–
652 for other mentions of the letters in the correspondence. AT IV 180 ªnds reference to
the Plempius letters in the Descartes-Voetius debate from the Admiranda methodus of Mar-
tin Schook.

26. Fundamenta medicinæ (1644), 115A: “Primum mihi inventum hoc non placuit, quod
et voce et scripto publice testatus sum, sed dum postea ei refutando et explodendo
vehementius incumbo, refutor ipse et explodor; adeo sunt rationes ejus non persuadentes,
sed cogentes: diligenter omnes examinavi, et in vivis aliquot canibus eum in ªnem a me
diffectis verissimas comperi.”

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408

Descartes on the Heartbeat

conversion for the medical world.27 Plempius also published here, für die
reader to judge for himself, Descartes’ letters to him in their entirety.

Although Plempius cites only Harvey as having convinced him, Die
context of the heated discussion with Descartes during this time should
have played a signiªcant role in his making up his mind.28 This has led
most commentators to conclude that it is the exchange with Descartes
that convinced Plempius accept to the theory of the circulation, sending
to Plempius’ letter to Descartes from March 1638, where he showed him-
self satisªed with the answers.29 The basis for this assessment is too thin in
my opinion to be conclusive.

zuerst, the phrasing of Plempius in the March 1638 remark, “neque ea
sententia valde displicet,” suggests to me that his opposition to the circu-
lation of the blood at that time was not so strong to begin with. Plempius
has a schoolman’s mind: the objections he brings against the circulation,
after hesitating to do so at Descartes’ invitation, should be taken in a scho-
lastic context, where exposing objections does not necessarily entail an
assent to those objections. This is conªrmed by his retraction when Des-
cartes proposes to publish the exchange: Plempius agrees to the publica-
tion, but he asks Descartes to leave out his objections concerning the cir-
culation. Descartes, reluctant to do so, proposes to insert a mention that
would say that those objections were made “animi gratia” and only in or-
der to satisfy Descartes’ request, and not because Plempius thought them
to be true.30 The same factor should be taken into account when assessing
the published textbook. Zweitens, in his public confession from 1644,
while publishing Descartes’ letters in their entirety, Plempius does not

27. See Harvey (1653), Wood’s preface, P. 12, on Plempius’ conversion: “Here is a great
change in his judgment. Hence I begin to hope for equity in others, that laying aside all
hatred, and acknowledging their error, they will at last with Plempius begin to think
well of Harvey.” Wood quotes the entire passage from Plempius (S. 11–12).

28. Idem. On Walæus’ experiments with ligatures conªrming Harvey (1641), see Pagel
(1976), S. 113–135. Plempius, a Dutchman, probably made Walæus’ acquaintance while
in Leiden or in Amsterdam in the early 1630’s.

29. Fuchs (2001), P. 129: “In fact, Descartes was able to persuade Plemp to accept
Harvey’s doctrine of the circulation.” Grene, “Translator’s Forward” to Fuchs (2001), P. xii:
“Indeed, Plemp, who had raised numerous objections to the notion of the circulation, War
converted, presumably by Descartes’ arguments (and observations!)” Gorham (1994),
P. 216, N. 22: “Descartes eventually manages to convert Plempius on the circulation hy-
pothesis.”

30. “Quantum vero ad eas, quæ spectant circulationem sanguinis, quas velles me
omittere, faciam omnino in hoc prout tibi visum fuerit; verum certe illas pluris facio,
quam tu, et merito possum inter validissimas, quas acceperim, reponere; quapropter si
velles, mallem nihil immutari; nisi si verba quædam hic illic, prout erit in rem, inserantur,
quibus proªtearis te animi gratia, aut a me rogatum illas proponere, potius quam quod
illas veras existimes.” AT II 344. This is a reply to a lost letter from Plempius.

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Perspektiven auf die Wissenschaft

409

rest his change of mind on Descartes’ arguments against his objections.
He never mentions Descartes as having convinced him in any way, al-
though he certainly had the opportunity to do so. Nor do his contempo-
raries read him as someone who had been inºuenced by Descartes on
the matter: Jean Riolan, when presenting Plempius’ account of the circu-
lation right after that of Descartes, does not send back to Descartes,
but invokes Plempius’ experiments, “quae sunt ab Harveo et Vallaeo
proposita et observata” (Riolan 1649, P. 45). The section on circulation
from Plempius’ Fundamenta of 1644 contains no trace of Descartes
(S. 115–118). He quotes 1) Harvey; 2) Johannes Walaeus, who published
his experimental results conªrming Harvey in 1640, and whom he knew
from Leiden; 3) his own scholastic exercises trying to refute Harvey, In
writing and in the classroom; Und 4) his vivisections. The exchange with
Descartes contributes to 3): it is one of the factors in a more complex pro-
Prozess. Between the exchange with Descartes over the circulation and the
public conversion in the Fundamenta of 1644, Plempius nevertheless pub-
lished the ªrst edition of the Fundamenta in 1638, where he continued to
doubt Harvey. Granted, the circulation of the blood and Harvey’s contri-
bution had gained a lot more exposure by 1644 than they had in 1638,
and perhaps Plempius, as a newly minted professor, could not allow him-
self to approve of the doctrine in 1638, but could do so in 1644. Thus in
1638 Plempius told Descartes that “this opinion does not really displease
me,” that he had only made those objections “animi gratia,” while at the
same arguing against the opinion in his book. There is no other exchange
between him and Descartes from 1638 Zu 1644, so that no other argu-
ments for the circulation are brought forward from Descartes’ side. More-
über, when Plempius decided to publish Descartes’ letters in 1638, Er
chose to leave out precisely his arguments for the circulation of the blood.
If Plempius revised his opinion in 1644 while meditating on Descartes’
arguments from 1638, which he decided to leave out in the Fundamenta
1638, there is no trace of this in his writings. Descartes’ arguments for the
circulation of the blood may very well have contributed to Plempius’ con-
Ausführung, together with other factors; but they can hardly be seen as the
decisive factor.31

Whatever the reasons behind the conversion, it is the way in which
Plempius presented it that mattered, and he gave the entire credit to
Harvey. Plempius chose to publish Descartes’ letters in 1638 truncated: Er

31. I am in agreement with French (1989), P. 79, who derives from extrinsic arguments
(the medical tradition to which Plempius was faithful) that Plempius “has been won over
by Harvey, not by Descartes.” My view is stronger than French’s: that it is the confronta-
tion with Descartes that pushes Plempius to embrace Harvey, via the heartbeat issue, as a
way to counter a perceived materialism in Descartes.

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410

Descartes on the Heartbeat

only retained the arguments concerning the origin of the motion of the
heart, and left out completely the arguments concerning circulation itself.
What interested him in 1638 in this exchange with Descartes was not
the circulation: it was the motion of the heart. The second edition of the
Fundamenta medicinae (1644) displays an extensive attack against Des-
cartes’ account of the motion of the heart in favor of a Galenic “pulsiªc
faculty.” The ªfth chapter of the second book is devoted to the “vital fac-
ulty” and is subtitled: “the motion of the heart is caused by the puls-
iªc faculty, not by the fermentation of the heart, against Aristotle and
Descartes.”32 In addition to reporting the arguments from the letters,
Plempius clariªed his position against Descartes in important ways in this
second edition. His new argument here is the following. There are two
separate contrary motions in the heart: a contracting and a distending mo-
tion. This would call for a redoubling of the pulsiªc faculty: a contracting
faculty and a distending faculty. He admits though that there can be
no distending faculty, since the dilation of the heart can be explained
through the inºux of the blood, as per Harvey’s demonstrated circulation.
It remains nevertheless to explain the contracting faculty: rejecting the
Cartesian “vaporization” of the blood, Plempius can still hold that for
the systole one needs to pose a pulsiªc faculty, like the one we have in the
muscles (P. 160).33 Thus the motion of the heart is entertained by this
pulsiªc faculty, contracting and releasing the cardiac muscle.

Plempius correctly identiªed both Harvey and Descartes as adversaries
of the Galenic “pulsiªc faculty” (P. 150); but he chose to argue at length
against Descartes, not against Harvey, and his argument drew heavily
from Harvey’s analysis of the systole. Harvey showed how the heart works
rather by contracting than by dilating the chambers, and how the violence
of the blood’s exit is the main driving force of the circulation. Plempius’
Streit, at face value, weighs against the rhythmical pulsiªc faculty of
the Galenists just as much as that of Harvey: there is no rhythmic dilation
and contraction due to a pulsiªc faculty, but there is contraction. What he

32. “Quid facultas vitalis. Est duplex: utraque dici potest naturalis facultatas. Motus
cordis sit a facultate pulsiªca, non a fervore sanguinis, contra Aristotelem et Cartesium.
Harvei sententia vera de motu arteriarum. Facultas pulsiªca duplex in corde.” Fundamenta
medicinæ (1644), 150B. For the pulsiªc faculty (which causes the muscle of the heart to
move simultaneously with the motion of the arteries), see Galen, De usu partium, lib. VI,
cap. XVII.

33. Cf. Harvey’s text from De motu cordis: “From these particulars it appears evident to
me that the motion of the heart consists in a certain universal tension–both contraction in
the line of its ªbres, and constriction in every sense. It becomes erect, hart, and of dimin-
ished size during its action; the motion is plainly of the same nature as that of the muscles
when they contract in the line of their sinews and ªbres.” Trans. R. Willis in Harvey
(1989), P. 22.

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411

adds to Harvey is a proper cause for the contraction, one which Descartes
himself had identiªed with a “pulsiªc faculty” when reading Harvey. Für
Plempius, Harvey is the via media. Just as Descartes had read the pulsiªc
faculty in Harvey’s forceful systole, Plempius effectively uses the same
reading as a way to counter Descartes. His conversion to Harvey in 1644
enhances his position against Descartes on the matter of the heartbeat,
which can be seen as yet another motive behind his choice for Harvey’s
version of the circulation.

A second historical detail of the 1644 publication of the Fundamenta is
telling for the follow up of the exchange. The precise instrumental cause
for which Plempius published Descartes’ letters here was that he was sum-
moned to do so by one of Descartes’ disciples at that time: Henricus
Regius. The second publication of the letters was not meant to support his
conversion as coming out of the exchange with Descartes, as one would
have thought: he only published the exchange again as an answer to
Regius’ interpellation.

Descartes was left in August 1638 with no reply from Plempius con-
cerning the plans for the publication of the exchange, and he did not learn
of the publication of extracts of his letters in the 1638 Fundamenta until
later in the spring of 1640, when Henricus Regius, at the time Descartes’
close disciple and early promoter of Cartesianism in the Northern Nether-
landet, sent him a letter informing him of the matter. The letter is now lost
Aber, according to Baillet, Regius reported on the matter in terms difªcult
to reproduce.34 Not only so, but Regius set out to hold in Utrecht a dispu-
tation on the circulation of the blood defending Descartes’ account of the
heartbeat. Before sustaining the disputation, Regius sent his theses to
Descartes for approval, and Descartes made comments on each of them
(see AT III 726). The disputation took place on 10 Juni 1640, durch
one of Regius’ students, Johannes Hayman. In the text of the printed the-
ses, Regius reported Plempius’ dishonest publication of 1638 of Descartes’
letters to him in harsh terms.35

34. Monchamp (1886), P. 137, states wrongly (and uncharacteristically for his usual ac-
curacy) that Regius wrote the letter to Plempius, citing Baillet. Baillet (1691), Bd. 2,
S. 36–37 is explicit on the fact that Regius wrote to Descartes, not to Plempius:
“M. Regius fut outré d’une conduite si malhonnête, et ayant confronté son livre avec les
réponses que M. Descartes avait faites près de deux ans auparavant à ses objections, il ne
put retenir l’indignation qui lui ªt prendre la plume pour en marquer ses ressentiments à
M. Descartes. Les couleurs qu’il donne dans sa lettre à l’ingratitude et à la mauvaise foi
de M. Plempius sont si vives, qu’on ne peut les exprimer de sa langue en la nôtre sans
entrer dans de semblables transports de colère contre une conduite si lâche.”

35. Disputatio medico-physiologica pro sanguinis circulatione (. . .) sub præside D. Henrici De
Roy (. . .) Exercitii gratia, Publice defendere conabitur Iohannes Haymannus (. . .) ad diem 10.
Iunii (Utrecht: 1640). The text is reprinted in AT III, S. 727–734.

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412

Descartes on the Heartbeat

Regius’ disputation gave Descartes’ account of the motion of the heart
almost exactly as per the Discourse (thesis III, AT III 728–729). It also
quoted a passage from Aristotle’s De Respiratione, 20, about the heart’s
pulse as an ebullition, to support Descartes’ account (AT III 730). Das ist
the same passage quoted by Plempius in his ªrst letter to Descartes on the
circulation (AT I 497). In a clever re-appropriation, Regius thus took up
the passage from Plempius, with Descartes’ approval, as a support for the
Cartesian account of the heartbeat. Nächste, in thesis VII, Regius held a para-
graph vilifying Plempius’ publication of Descartes’ letters: “He partly
mutilated and perverted the responses at objections and instances, and he
omitted some. Such that whoever will compare his account with the let-
ters written two years before this publication, will be able to tell.”36 Des-
cartes had instructed Regius to put his true name, “Descartes.” instead of
the Latin Cartesius, and had asked him to temper his adjectives and to
give examples of the mutilation (AT III 68). Regius conformed to the rec-
ommendation only partly.

This disputation is quoted by Plempius in the Fundamenta of 1644
when publishing anew Descartes’ letters, this time unabridged. His ges-
ture here is an answer to the Descartes-Regius attack from the disputation
von 1640.37 It is thus through Regius that the dispute with Descartes con-
tinued in 1644, and Plempius answered to this renewed attack from
Descartes’ side. Regius’ involvement and Plempius’ 1644 edition makes
explicit the shift of the dispute from the issue of the circulation of the
blood to the more theologically informed issue of the cause of the heart-
beat. What started in 1638 as a dispute over the theory of the circulation
of the blood became by 1644 a dispute over the status over the powers of

36. AT III 732: “Hanc verissimam Viri Nobilissimi et Incomparabilis D. Renati des
Cartes sententiam nuper litteris familiaribus labefactare conatus est Plempius in Lovanensi
Academia Medicinæ Professor. Quamvis autem sollidissime ad argumenta, quæ proposuit,
ipsi sit responsum, et plus quam satisfactum: placuit tamen ipsi rem privatim actam,
inscio Renato, publicam facere Doctorumque circulo arbitrandam subjicere. Ut itaque
Disputationis hujus Moderator etiam suum hic interponat arbitrium, videtur non tantum
per compendium (ut ipse ait), sed cum veritatis dispensio, nec satis bona ªde, res ab ipso, in libro
quem Medicinæ Fundamenta appelat, fuisse ennarata: Responsiones enim ad objectiones et
instantias, partim mutilaverit et pervertit, partim artiªcio quodam præteriit.” Emphasis
added.

37. “Quod non tantum per compendium (ut ego ais) sed cum veritatis dispensio, nec satis bona
ªdem responsiones ennaraverim, ac partis eas mutilaverim et perverterim, partim artiªcio quodam
praeterierim.” Fundamenta medicinæ (1644), P. 152A, emphasis in the original. This is a direct
quote from Regius’ disputation quoted in the previous note (AT III 732). Cf. Descartes to
Berwerwijk, 5 Juli 1653, where he complains again about Plempius in the same terms:
“Sed nonnullæ objectiones, ad ipsam pertinentes, mihi missæ sunt Lovanio ante sex annos,
ad quas tunc temporis respondi, et quia earum auctor meas responsiones mala ªde distortas
et mutilatas in lucem edidit.” AT IV 6, my emphasis.

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413

the soul. The Fundamenta (1644) continued to defend the positions on the
functions of the soul expressed by Plempius in his 1638 letters and ex-
panded on them. In the letters, Plempius had given a vivid idea of how
the life-responsible “faculty” of the soul operates (a “vivifying spirit”): eins
can see it in freshly extracted hearts, or in freshly beheaded bodies, welche
continue to function and even digest food in virtue of the soul’s lingering
“spirit.” The Fundamenta of 1644 presents the same “facultas vitalis” as a
faculty of the soul. It is in fact now duplex: viviªcatrix, which produces the
vital spirits, and pulsiªca, which entertains the motion of the heart by pro-
voking the systole (Fundamenta 1644, P. 150). Gleichzeitig, he did
not shy away from acquiescing to Harvey’s mechanical explanation of the
motion of the arteries (P. 160) and to his explanation of the diastole. Es ist
not mechanism by itself that Plempius resists, but precisely the rejection
of the “pulsiªc” faculty as a source of motion. As he told Descartes in
1638, both of them carry amphorae impregnated with different odors.38
Der 1644 publication looks like an anti-Cartesian treatise.

Descartes’ use of Regius in the debate warrants more consideration for
the history of the reception of his account of the heartbeat, because Regius
did not always conduct himself as docilely as in this attack. Through his
reactions to Plempius and his sustained series of publications radiating
from the northern Netherlands, he can be seen as a catalyzer for the pre-
cipitation of the Leuven affair, precisely because of his growing heterodoxy
with respect to the medical establishment while professing Cartesian-
ism. From proposing a radicalized version of Descartes’ physiology in the
1640s and giving a summa of Cartesianism that Descartes never wrote
(Fundamenta physices, 1646, with enlarged editions in 1653 Und 1661)
Regius would evolve to depart from Descartes and eventually oppose him
with an alternative account of the motion of the heart.

Already in the lost letter reported by Baillet, von 1640, Regius is re-
ported to have questioned Plempius’ understanding of the Cartesian ac-
count of the cause of the heartbeat: “Where Mr. Descartes reports multiple
causes which, taken together, produce the heartbeat, Plempius only re-
tains one of them, namely heat.”39 This phrase testiªes for the ªdelity of
Baillet’s report on the letter, as indeed Regius will continue in his publica-
tions to report a number of “secondary causes” for the heartbeat.40

38. “Sed tamen aliter sentimus, quia dum testæ recentes eramus, alio odore imbuti

fuimus, quem servamus.” AT I 400.

39. Baillet (1691), Bd. 2, P. 37: “Qu’à l’endroit où M. Descartes rapporte plusieurs
causes qui jointes ensemble produisent le battement du cœur, Plempius n’en rapporte
qu’une qui est la chaleur.”

40. On Regius, see De Vrijer (1917); Verbeek (1988), (1992), (1994); Gariepy (1990);

Alexandrescu (2012), S. 155–186.

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414

Descartes on the Heartbeat

In a second disputation he sustained in Utrecht on the circulation of
the blood, Im April 1641, Regius gave the Cartesian heating account
(coctio) as the cause for the motion of the blood, with a twist: there occurs a
“sanguiªcation” in the heart through the process of a “pulsiªc ebulition.”41
The “pulsiªc ebullition,” not a Cartesian notion, is nothing more than a
barbarism meant to replace Plempius’ “pulsiªc faculty” with chemical eb-
ullition. Descartes comments on Regius’ phrasing and speaks of a “general
coctio” (AT III 67), but he will not use this phrase in the accounts pub-
lished in the Passions of the Soul or in the Description. One “sanguiªcation.”
following Regius, occurs through ebullition in the right ventricle, und ein-
other one in the left ventricle. The cause of the motion of the heart and ar-
teries, while it consists essentially (causa continens) in the ebullition of the
blood already found in the heart before the new blood ºows in, relies nev-
ertheless on a fourfold complex of concurrent, helping causes: 1) the “apti-
tude” and the composition of the blood; 2) the heat of the heart; 3) Die
part of the blood which remains in the heart after the beating to act as a
ferment; 4) the disposition of the vessels of the heart; Und, he adds, “not
[An] some particular pulsiªc faculty located in the heart and communi-
cated by it to the arterial walls.”42 This disputation was still directed
against Plempius, who had maintained a pulsiªc faculty communicated
through the arterial walls in his letters to Descartes and in his Fundamenta
medicinae (1638).

In his Fundamenta physices (1646), Regius presented the account of the
motion of the heart, as a good Cartesian, in the chapter on animals.43 He
restated the four remote causes from the 1641 disputation, but added as a
second proximate cause for the heart’s motion, alongside the rarefaction of
the blood: the animal spirits gathered in the ªbers of the heart.44 The ad-

41. “In corde ªt coctio, cum chymus sanguini a reliquo corpore ad cor redeunti
permistus, et simul cum eo in Hepate præparatus, in verum et perfectum sanguinem, pro
ebullitionem pulsiªcam, commutatur.” Physiologia (1641), 20, in Bos (2002), P. 213.

42. “Admirandus igitur ille Cordis arteriarumque motus, præter sanguinis in corde
existentis ebullitionem, quæ causa ejus continens est, a quatuor antecedentibus perªcitur
causis; primo a sanguinis cor ingredientis ad dilatationem aptitudine; Secundo a cordis
calore: Tertio a parte sanguinis, quæ post singulos pulsus ardens, aut tanquam fermentum,
in corde remanet: quarto a cordis vasorumque ipsius conformatione; non autem a peculiari
facultate pulsiªca cordi insita, et arteriarum tunicis ab ipso communicata.” Physiologia
(1641), 21 in Bos (2002), P. 214.

43. P. 181. The chapter treats of animals in general, and then we get separate chapters

on irrational animals (De Bestiis) and rational animals (De Homine).

44. “Itaque admirandus ille cordis arteriamque motus, præter sanguinis in corde ex-
istentis rarefactionem, spirituumque animalium in ªbras cordis inºuxum, quæ eius causæ
sunt proximæ, etc.”, idem, P. 181.

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415

dition of the motion of the spirits in the account of cardiac motion is a de-
velopment that seems Cartesian in spirit but not in littera: the motor ac-
tion of the animal spirits, although recognized by Descartes, is never
taken by him to be a cause of the circulation. The propagation of the blood
through the entire body is accounted for mechanically as the communica-
tion of motion (both the motion of the blood and that of the spirits) down
to every vessel, and this explains how some dying people continue to ex-
hibit a spontaneous contraction and expansion of sanguine vessels, al-
though their heart and their blood ºow had stopped.45 At this stage, Das
can be seen as a development building on Descartes, in tune with the con-
temporary trends in the medical discourse; Descartes will present himself
a developed account of the motion of animal spirits in his Passions of the
Soul of 1649.

The letter from 1640 that Baillet reported already suggested this devel-
opment, as we have seen. But there is one further evolution in Regius’
physiology, which makes him less of a follower of Descartes. Up to 1661,
his account for the origin of motion in the heart consists in Cartesian fer-
mentation plus this agitation of the animal spirits, a double cause, sus-
tained by certain dispositions found in the cardiac apparatus. However in
the third edition of his Philosophia naturalis, von 1661, Regius introduces a
passage arguing that the agitation of the animal spirits is the “principal”
(praecipua) cause for the circulation, for the fermentation of the blood is too
weak to push the blood throughout the body. He argues now explicitly
against Descartes’ account: “it is not the rarefaction of the blood in the
heart, but instead the movement of the animal spirits in the ªbers of
the heart, that which should be taken as the main cause between the prox-
imate causes of the pulse.” And he develops:

Among the proximate causes of the motion of the heart, the main
eins, established here with necessity, is the very powerful ºow back
and forward of the animal spirits from the brain through the nerves
in the ªbers of the heart; for the rarefaction, the effervescence or the
swelling of the blood which generally takes place in the heart is too
thin, and thus too weak to be the main proximate moving princi-
Bitte, and much less the only one, needed to push and repel all of the
blood from the heart back and forward, through all of the arteries
and veins of the animal (as Aristotle in his De Respiratione and
Descartes in the Discourse on Method state).46

45. Idem, P. 182.
46. Philosophia naturalis (1661), S. 305–306: “Inter causas proximas cor moventes,
præcipua, et necessario hic statuenda, est satis validus spirituum animalium e cerebero per

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416

Descartes on the Heartbeat

Let me venture an interpretation: Regius’ addition of the ºow of the spir-
its as a concurrent cause for the motion of the heart, and subsequently
as its main cause, is meant to counter increasing attacks against Des-
cartes’ account with an alternative mechanical explanation.47 Regius con-
tinued Descartes’ project to replace Aristotelian-inspired Galenic phys-
iology with mechanism, be it with certiªed Cartesian explanations or
nicht. Seventeenth-century Aristotelian physiology of the soul maintained a
number of proximate causes subordinated to the original motor cause, Die
sensitive soul. Regius’ strong materialist developments made clearer Des-
cartes’ opposition to the traditional Aristotelian views on the soul by ex-
plicitly using Aristotelian jargon. Dabei, he read closely the formula-
tions of Aristotelian physiology and replaced every one of them with
Cartesian ideas, including the Aristotelian complex of proximate causes
subordinated to one primary cause. “The life of the animal,” Regius says,
“or its vivifying faculty (facultas vivendi), consists in this, that there is in
it a certain part equipped with ªre, which is called the heart, so hot that it
heats up the nourishing juices ºowing through the veins and parts of
them are pushed out through the arteries, and then, after they are heated
wieder, these juices ºow back to the heart through the connected veins,
continuously.” Circulation is thus not more, nor less than what the faculty
of life consists in, sustained by the heat of the heart. More of this: “The
faculty of sense and movement, that people call the sensitive soul, ist der
arrangement and conformation of the parts of the animal in spirits, nerves
and other sensitive organs,” etc. (my emphasis).48

nervos in cordis ªbras reciprocus inºuxus: cum rarefactio, effervescentia, sive intume-
scentia, sanguinis, quæ communiter in corde ªt, sit tantum exigua, et proinde nimis
debilis, quam ut totum sanguinem, per totius animalium corporis arterias et venas, A
corde et ad cor reciproce, tanquam præcipuum, nedum solitarium, (ut Aristoteles lib. von
respirat. et Cartesius discurs. de Method. statuunt), proxime movens principium, pellat atque
repellat.”

47. The passage I bring forward from the 1661 edition should be added to Thomas
Fuchs’ account of Regius’ physiology of the heart (Fuchs 2001, S. 146–148). Regius’ ad-
dition is distinctly intercalated as a paragraph into text from previous editions. Während
Fuchs does bring forward Regius’ account of the animal spirits as a concurrent cause for the
motion of the heart, he fails to add Regius’ anti-Cartesian stance from 1661, and reads him
as a Cartesian throughout. See also de Vrijer (1917), P. 215 “In zijn grootere werken heeft
Regius die cartesiaanische physiologie bijgehouden,” etc.

48. Fundamenta physices (1646), 153: “Vita animalis, seu ejus vivendi facultas, in eo
consistit, quod quædam in eo sit pars igne, tantum calido, instructa, quæ cor dicitur, In
quam alimentarius succus per venas inºuens incalescit, et in partes alendas per arterias
impellitur, ac deinde, ut rursus incalescat, per continuas venas ad cor perpetuo reºuit. [. . .]
Facultas sentiendi et movendi, quæ anima sensitive vulgo dicitur, est partim animalis in
spiritus, nervos, et alia sensoria [. . .] attemperatio et conformatio.”

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417

Regius continued to push his anti-Aristotelian physiology through
the 1660s explicitly against Descartes. Descartes had always been careful
not to openly provoke the Aristotelianism of the schools, largely by ignor-
ing its theses in his published work. It is precisely Regius’ open attack
that guardians of orthodoxy such as Plempius feared from the Cartesian
mechanical explanation of the cardiac motion: it undermined the hylo-
morphic structure of living bodies that was the framework and reference
for their medical science. Not long after the quarrel with Plempius of
1640, Regius acquired a reputation for endangering the union of the
body and soul by defending an accidental psychophysical union, welche
stirred a heated and famous controversy in Utrecht throughout the 1640s
and occupied much of Descartes’ energy for the remainder of his life.
The Utrecht quarrel must have had a certain echo in Leuven. The Leuven
theological reactions to which I turn next are best seen against Regius’
move of developing from Descartes’ physiology an upfront attack against
Aristotelianism.

4. Libertus Fromondus (1587–1653) and the Leuven condemnations
(1662–1663)
When Plempius received the Discourse and Essays in 1637, he forwarded
one copy to his colleague and former teacher, Libertus Fromondus, as in-
structed by Descartes.49 Fromondus was a good candidate for Descartes to
win over, as the head of theological studies at a powerful Catholic univer-
Stadt. He was also a respected man of science. Von 1637 he had an estab-
lished reputation as a defender of the integrity of the Catholic body of
knowledge and was certainly the voice to be feared at Leuven from the
Aristotelian camp.50

Fromondus replied to Descartes rather bluntly and dismissed him as an
atomist—as courtly and mischievously as possible. He even sent him a
treatise against atomism he had written.51 Granting him, almost sarcasti-
cally, the glory of a second Pythagoras or Epicurus in his endeavor to put

49. Plempius calls Fromondus his “parent” (parens), AT I 399.
50. Fromondus has played his part in the history of Jansenism: disciple and intimate
friend of Cornelius Jansenius, he helped with the revision and publication of the Augustinus
and was engaged in a famous controversy with the Calvinist Gijsbertus Voetius in 1635–
1636 on Jansenist theses. He had come close to heresy yet again in his youth in a tortuous
seduction story with Galileo and Copernicanism, ªnishing by notoriously refuting both.
See Pantin (2001). On Fromondus’ career, besides Monchamp, see Ceyssens (1963) Und
Garber (1988). Fromondus held the chair of theology in Leuven since 1634, before having
passed through the chairs of rhetoric and philosophy.

51. Labyrinthus sive de compositione continui (Antwerp 1631). The book is used by Leibniz
as a compendium of arguments in the Nouveaux Essais (2, 23, 31) and the Essais de théodicée
(Discours préliminaire, 24).

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418

Descartes on the Heartbeat

all science on an entirely new track, he also added that, as clear as the au-
thor’s ingenuity was, as obscure was the truth in his writings. He feared
that Descartes may fall into the “crass philosophy” of Epicurus, without
realizing it.52

Fromondus brought forth 18 articles of contention: three on the gen-
eral philosophy of the Discourse, six on the Dioptrics and nine on the
Meteors. First of all, it is the approach that fails: the reduction of real quali-
ties to the mechanical principles goes sometimes too far.53 As he moved on
to attack Descartes’ explanations throughout the book, he raised objec-
tions to animal automatism and to the Cartesian theory of sensitivity. Ob-
jecting to the mechanics of the heart as responsible for bodily sensations,
his concern was for safeguarding the sensitive soul: “the heat of the heart,
without it being a sensitive soul, can exert in the body all the functions of
the sensitive soul, apart from those of the rational soul.” And he continued
in proper Aristotelian parlance:

Er [Descartes] seems to say that heat, as that from heated hay, can
exert in the human body all the animal operations, except for the
operations pertaining to the rational soul. Thus the heat of the hay,
without any other sensitive soul, can see, hören, usw. Such noble oper-
ations do not seem to be able to proceed from such a humble and
brute cause.54

One could push this line of argument and ask why would the heat of the
hay not make the hay itself see and hear? Descartes would probably answer
that this is precisely what happens, once a certain level of complexity in
the organized matter is achieved (the machine metaphor). The issue at
stake is double: Descartes’ account cancels both the divide between the
sensible world and the material world and that between the sensible ani-
mals and the rational ones. The second consequence is more threatening

52. Descartes publicly tries to save face, saying to Huygens that “the dispute between
us was more like a game of chess; we remained good friends”, AT II 660. Cf. AT I 449: “Et
en effet je me réjouis, lorsque je vois que les plus fortes objections qu’on me fasse, ne valent
pas les plus faibles de celles que je me suis fait à moi-même, auparavant que d’établir les
choses que j’ai écrites.” He does sends to Huygens though the replies he had given to
Fromondus and to which the latter did not deem to answer, and at some point contem-
plates their publication—as per the letter to Plempius from AT II 345.

53. AT I 408: “Nimis multa sperat se expediturum per solum situm, aut motum

localem, quæ sine realibus qualitatibus aliis non possunt, aut nihil intelligo.”

54. AT I 403: “videtur dicere quod calor, qualis in fœno calefacto, possit exercere
omnes operationes animalis in corpore humano, exceptis actionibus propriis animæ ration-
alis. Ergo calor fœni, sine alia anima sensitiva, potest videre, audire, usw. Tam nobiles
operationes non videntur posse prodire ex tam ignobili et bruta causa.”

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Perspektiven auf die Wissenschaft

419

for Fromondus. Descartes’ mechanics of the heart and the reduction of the
animal soul opens the path to a dangerous materialism: if one says that
some of the operations normally attributed to the soul actually take place
as a result of the functioning of a mechanism, then we are in danger of ex-
plaining all operations of the soul, including its purely intellectual ones,
through this mechanism. It “opens the way to the atheists, so that similar
causes [motion provoked by heat] are assigned to the rational soul.”55
He preemptively congratulated Descartes at the end of his letter for still
holding the thesis of the immortality of the soul, as if it were something
to be congratulated for, somewhat in spite of his other commitments.56
Fromondus’ worries will take a clear shape shortly after, in the writings of
Henricus Regius, as we have seen earlier.

Descartes himself would, Jedoch, painstakingly keep away from such
impious implications. Since the matter is not only about the physiology of
the heart, his avoidance of materialism and struggle to stay away from her-
esy will lead him to argue for the explanation of cardiac motion through
a theory of the operations of the soul and a theory of sensations. Des-
cartes undertakes for Fromondus this route, only too brieºy. The explana-
tion of the vision without intelligence, which Descartes puts forward for
Fromondus as a reply to his suspicions of heresy, is the best argument that
Descartes makes in this exchange and the key to his defense. He argues
that mechanically explained sensations, such as those we ªnd in animals,
are not the same as sensations explained through the psychophysical union
in man, which display the work of the rational soul:

Er [Fromondus] supposes that animals see just as we do, i.e. Sein
aware or thinking they see, which is said to have been Epicurus’
view and is still almost universal. Aber [. . .] I explain quite explic-
itly that my view is that animals do not see as we do when we are
aware that we see, but only as we do when our mind is elsewhere.
[. . .] In such a case we too move just like automatons, and nobody
thinks that the force of heat is insufªcient to cause their move-
ments.57

55. “Hinc etiam fortassis via sternetur atheis, ut etiam animæ rationalis operationes
simili causæ tribuant, et eam corpore humano excludant, aut saltem materialem animam
vice immaterialis nobis infarciant.” AT I 403.

56. “Delectat etiam me magis quod ªde catholicus et spem nobiscum habeat post hanc

vitam brevem æternæ.” AT I 408.

57. AT I 413 / CSMK 62. Cf. the Replies to Hobbes, on the distinction between im-
ages and thought, esp. Descartes’ reply to Hobbes’s sixth objection, AT VII 182 / CSM II
128: “brute beasts cannot afªrm or deny, even in thought; and hence cannot make judg-
gen,” etc.

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420

Descartes on the Heartbeat

Außerdem, Descartes continued, the animal soul (i.e. the Aristotelian
vegetative and sensitive functions) is nothing else but pure blood, and he
conveniently and heavily cites the Bible on that.58 There is no soul-like
faculty that would give rise to motion in living bodies, and hence Des-
cartes’ physiology of the heart is warranted to posit a naturally mechanical
source of motion. Fromondus’ point is to say that postulating this conti-
nuity between beasts and man through the mechanical physiology of the
heart gives way to a dangerous materialism. Descartes’ response is, on the
one hand, to make clear where the line stands between the corporeal func-
tions and the operations of the rational soul, and on the other hand to
counter-attack by turning Fromondus argument against him, showing
how his own account is the orthodox one and the Aristotelian conception
of the soul is the truly heretic one: “Since these people posit so little differ-
ence between the operations of a man and of an animal, I do not see how
they can convince themselves there is such a great difference between the
natures of the rational and sensitive souls.” He even offers a rare critique of
the conceptual inconsistency of a sensitive soul: “On their view, Wann
the sensitive soul is alone, its nature is corporeal and mortal; when it is
joined to the rational soul, it is spiritual and immortal.” Its functioning
approaches ridiculousness: “it seems that on their view sensation in ani-
mals is closer to cognition in God and the angels than human reasoning
is” (AT I 415 / CSMK 62).

Fromondus is not alone in warning of the danger of Descartes’ physiol-
Ogy. Gassendi, Hobbes, Bourdin or the sixth objectors, they all make the
point that denying the animal soul and mechanizing the human sensitive
soul is endangering the gap between animal and man and is offering to an
atheistic mind the opportunity to extend that mechanism to the very op-
erations of the rational soul. Descartes will dismiss this as a misunder-
standing of the scope of his project, but the stigma remained. Jedoch,
the proposal of a mechanistic vital principle—heat, or fermentation—is
not only a dangerous step towards mechanizing vital functions, but can be
used with equal value as an argument for the psychophysical distinction,
a point which Descartes made to Fromondus. The argument will be
brought forward by Regius in his Fundamenta physices of 1646, and will
be used by Cartesian apologetics throughout the rest of the century:

It is certain that if we attribute to animals a sensual, imaginative or
any kind of intellect, be it a very low one, or any sort of cognition,

58. AT I 414 : “cum Sancta Scriptura ªrmiter credo et, ni fallor, dilucide explicui,
animas brutorum nihil aliud esse quam sanguinem, nempe illum qui, illorum corde calefactus et
attenuatus in spiritum, ab arteriis per cerebrum in nervos et musculos omnes se diffundit,”
usw.

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421

then there would be no natural cause through which one could say
that the human mind is less corruptible than the soul of a dog, A
fox or a monkey.59

Regardless of Fromondus’ opposition, by the end of the 1640s, Descartes’
major publications were on the market and Cartesianism was gaining
strength in Leuven. If professors like Arnold Guelincx, Gérard Van Gut-
schoven or Guillaume Philippi were professing Cartesian thesis, the oppo-
sition was still strong.60 In 1653, Plempius, holding his ground, initiated
a campaign to get Cartesianism ousted from the University. His efforts
amounted to not much: he sent a circular letter to a number of profes-
sors asking them to comment, censure and condemn Descartes’ writings,
and he published the letters he received as an appendix to his old anti-
Cartesian treatise, the Fundamenta (1653 edition: Doctorum aliquot in Aca-
demia Lovaniensi Virorum Iudicia de Philosophia Cartesiana, S. 375–387).
The intent was to gather personal attacks in the form of “censurae” from
Leuven professors, as a plea for an ofªcial condemnation of the Cartesians
in der Universität: will Leuven stand still and allow this new philosophy to
chase away its Aristotle, when Utrecht and Leiden have already con-
demned it?61

Plempius’ own letter serves as a preface to the small anti-Cartesian
tract. His starting point is that Descartes’ philosophy amounts to a re-
vival of Democritus and should be treated as such; the rest of the letters
are meant to detail this judgment. Out of the forgettable names that
Plempius recruited, we will retain Fromondus’ censorship as pointing out
in detail the theological danger posed by Descartes. Leaving aside the con-
tentious issue of the Eucharist, to which the bigger part of the letter is de-
voted, Fromondus nevertheless starts with combating the physiological
point of the non-existence of animal souls, which contravenes the Holy
Writ. The argument is interesting. The fact that the death of humans and
the death of mules is said to be unus by the Holy Writ (P. 379A, unus
interitus est hominis et iumentorum) entails according to Fromondus the fact

59. Fundamenta physices (1646), 242: “Et certe si bestiis sensualem, imaginativum vel
quemlibet alium etiam vilissimum intellectum, vel qualemcunque cognitionem attribu-
amus, nulla causa naturalis dari potest, cur hominis mentem magis, quam animam canis,
vulpis, vel simiæ incorruptibilem esse dicamus.” On Cartesian apologetics and the argu-
ments defending his conception of the soul, see Fowler (1999).

60. See Monchamp (1886), ch. XII (Arnold Guelincx), XV (Gérard Van Gutschoven),
XVI (Guillaume Philippi), et passim. Andererseits, the Carmelite professor François
Crespin (Bona-Spes) mentions in his Commentarii in universam Aristotelis Philosophiam
(1652) Descartes as having rejected substantial forms and “nec multum abest Fromondus”
(Monchamp 1886, P. 211).

61. Fundamenta (1653), 377B.

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422

Descartes on the Heartbeat

that the souls of humans and mules act as forma informans: the destruction
of man is the separation of the soul from matter, i.e. the end of the process
of in-formation of the matter by the soul; the Council of Vienne stated,
against the Averroists, that the human soul is a forma informans, not a forma
assistens, as the Cartesian-Democritean position could be interpreted; Das
entails that the soul of the mule is also a forma informans, informing mat-
ter, otherwise its destruction would not be the same with the destruction
of man (P. 379A). Fromondus was actually reºecting here on his exchange
with Descartes through Plempius (he states so himself, P. 378B) and he
answers through this argument to Descartes’ comment to Plempius men-
tioned earlier on the inconsistency of the Aristotelian position on death
(AT I 514). But Fromondus goes on to expresses a very lucid grief against
the Cartesians from his own university: in following Descartes, they fail to
teach their pupils about the range of faculties and vital functions of the
soul, things that are of utmost necessity if they are to progress towards
theological studies. Pupils understand Saint Thomas and the scholastics
easier, says Fromondus, just as they understand Galen in medicine easier,
because they treat the various powers and faculties of the soul at length.
Entering theology from a Cartesian training, one would be struck dumb
by the proliferation of functions and the paraphernalia of powers of the
soul needed there, and would not understand it, or worse, would become
reluctant towards it. This seems like a very old-school position from
Fromondus, a medieval view well alive in the middle of the seventeenth
Jahrhundert: physiology is not a science for itself; it should serve as a prepara-
tion to theology, and explaining the vital functions through motion alone
does not help. The enquiry as to whether the faculties are distinct from the
soul a parte rei or just objectively should be done in theology, not in physi-
ology; ansonsten, it is like a harvesting a ªeld too soon.62

Fromondus died before his letter appeared in print (In 1653), aber sein
anti-Cartesian position is consistent throughout his career from the mo-
ment he laid his eyes on Descartes’ writings. His publication of a textbook
on The Christian Philosophy of the Soul in 1649 should be weighed in this
anti-Cartesian context.63 Monchamp (1886, S. 151–156) takes out a
number of passages from this manual that seem directed against Des-
cartes, but the fact is that Fromondus never mentions Descartes’ name in

62. Fundamenta medicinæ (1653), P. 380B: “Interim adolescens philosophus S. Thomam
et Scholasticos in Theologia, Galenum et Medicos in vestra Medicina facilius intelliget, qui
de potentiis et facultatibus animæ tam multa et varia disserunt: ne adolescens, ubi ex ludis
illis philosophicis, qui per motus locales, aut sicsehabentias satis explicare conªdunt, Anzeige
superiores Scholas ascenderit, et de varia istarum animæ facultatum supellectile loquentes
audierit, obstupescat et sine conceptu remaneat”; vgl. Monchamp (1886), S. 253–256.

63. Philosophiæ Chrisitanæ de Anima libri IV (Leuven: 1649).

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Perspektiven auf die Wissenschaft

423

his published books.64 With his characteristic sensibility towards the an-
cients and from the high seat of his Leuven chair, Fromondus directs his
De Anima against the Democriteans of the day and their Epicurean disci-
ples, of various incarnations. This is not a polemical treatise; aber es ist nicht
hard to see in this publication a reaction to the danger of Cartesianism
creeping up in Leuven classrooms, if we look at it from the retrospective of
Die 1653 letter. The publication of the book, in those years, seems to act as
a theological complement to Plempius’ Fundamenta Medicinae.

In der Zwischenzeit, Rome itself became interested in the Leuven affair. An
3 Juli 1662 the Faculty of Arts of the University of Leuven held a meet-
ing debating the installation of Cartesian doctrines in the university, as a
response to an inquiry from the papal nuncio. It was only the beginning of
a series of such meetings. Im August, a bachelor student held and pub-
lished a series of Cartesian medical disputations. The Apostolic Nuncio,
having seen the student’s placard, wrote a warning letter to the university
rector, citing the Cartesian theses put forward there: “that the arguments
which give a soul to animals are not probable; that it is doubtful that ani-
mals live; that there is nothing new under the sun, except for the rational
soul, i.e. [. . .] that no other [kind of ] soul or qualities are produced anew,
because there are none.”65 The recently recovered reports by the censors in
Rome that motivated the decrees of condemnation issued by the Holy
Congregation of Cardinals in 1662 Und 1663 mention the same danger of
the lack of the animal soul. The report on the Passions of the Soul, of the
Roman censor Stephanus Spinula, alongside the condemnation of the ac-
count of the passions through the movements of the spirits, puts forward
as a censorship-worthy thesis the following: “that no movement of the
members of the body originates from the soul; and it is an error to believe
that the soul gives motion and heat to the body.”66 Plempius will report in
high spirits on the condemnation in his fourth edition of the Fundamenta
medicinae (1664), which by now has become almost the equivalent of a
journal series on anti-Cartesianism.67

64. Monchamp (1886), S. 151–156.
65. Letter of de Vecchi, in Monchamp 1886, S. 362–364 and Armogathe and Carraud
(2001), P. 130: “Argumenta quæ brutis animam asserunt, non esse probabilia. Dubium
esse an bruta vivant. Nihil sub coelo esse novi, seposita anima rationali—videlicet prout
intelligi puto ab Authore—nullas animas, nullas qualitates de novo produci, quia nullæ
sint.”

66. Armogathe and Carraud (2001), P. 112, give the text of the censure of Stephanus
Spinula: “3. Nullum motum corporalem membrorum oriri ab anima; quin erroneum esse
credere animam dare motum et calorem corpori.”

67. “C’est ainsi que ce qui a été commencé à Louvain par la sacrée Faculté de Théologie,
ªlle de l’Église romaine, appui du Siège apostolique, gardienne des dogmes véritables, a été

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424

Descartes on the Heartbeat

5. Abschluss
The widespread view of the unorthodoxy of the animal-machine doctrine
passed through the reduction of the sensitive soul that Descartes had ac-
complished in his account of the heartbeat. From this review of the anti-
Cartesian reception in “the Leuven affair,” assessing the motivation lead-
ing up to the condemnation of Descartes’ physiology should take into
account the following: the debate starts off with Fromondus’ and Plem-
pius’ letters from 1637–1638, drawing on Descartes’ physiology from the
Discourse; the exchange from 1637–1638 shifts quickly from an academic-
style dispute about the circulation of the blood to the philosophical impli-
cations of Descartes’ account of the heartbeat, where the real disagreement
Lügen; the concerted rejection of Descartes’ physiology from 1637–1638 will
be sustained by the two professors’ subsequent publications; Fromondus’
letter makes explicit the theological implications of Descartes’ account
on the heartbeat that Plempius opposed; Descartes’ debate with Plempius
over the heartbeat is continued through Regius’ disputations and publica-
tions from 1640–1641; Plempius’ use of Harvey’s analysis of the systole is
yet another way to counter Descartes, and his conversion to the circulation
of the blood theory should be seen against this background, rather than
as a victory of Descartes; Plempius’ anti-Cartesian campaign peaks in
the edition of 1653, with Fromondus’ theological condemnation. Endlich,
Rome conªrms Plempius’ efforts in 1662–1663.

Thomas Gariepy has shown that for the ªrst generation of Cartesians in
the Northern Low Countries it was the Cartesian reading of Harvey’s ac-
count of the circulation of the blood that represented “the cornerstone of a
mechanical physiology” (Gariepy 1990, P. 316). The Leuven reception
supports this view. When reading the ªrst reactions to Descartes’ cardiol-
Ogy, one assessment stands out: the medical explanation for the origin of
motion in the heart and blood sits at the core of Descartes’ project of re-
jecting the hylomorphic metaphysics of the Aristotelian sensitive soul,
and it is immediately perceived as an attack on the medical establishment
that went beyond the physiological matter. Descartes’ account is read
and discussed by careful defenders of the Aristotelian tradition such as
Plempius or Fromondus and as putting forward a materialist danger dis-
cernible very early in Regius. Harvey’s discovery of the circulation of the
blood will be drawn into this Cartesian controversy and will be used by
Aristotelian-minded physicians against Descartes, as Plempius does. Bei
this stage, Descartes’ argument for the theological good use of his physiol-

achevé par la sacrée Congrégation des cardinaux.” Preface to the 1664 edition, xx quoted by
Monchamp (1886), P. 392.

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Ogy, expressed also by Regius, does little more than put fuel on the ªre.68
This comes to show how far along a physiological account can go, und das
extent to which the propagation of Harvey’s discovery of the circulation of
the blood through Descartes is determined by theological constraints. Per-
haps unintentionally, Descartes is not far from historical clairvoyance
when saying that the acceptance or rejection of his explanation of the mo-
tion of the heart will determine the faith of his philosophical project.

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