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Robert Boyle

Philosophy of Spinoza

By Descartes, Ethics, Kabbalah, Leibniz, Maimonides, Robert Boyle
Baruch (Benedict) Spinoza (1632-77) was born at Amsterdam into a Portuguese Jewish merchant family. While still a young man, he was banished from the Sephardic community in Amsterdam, apparently because of his heretical views. He lived in the Christian world as an artisan, grinding optical lenses. His Ethics eventually became a classic of Western philosophy. 
A sceptical idea is associated with Spinoza’s early years at Amsterdam (Nadler 2002), i.e., the soul is mortal and dies with the body. In contrast, Maimonides and Gersonides (both Aristotelians) believed that the soul can live on after death, while retaining only intellectual faculties. Avoidance of “personal immortality” and damnation bears a close resemblance to the “acquired intellect” theory expressed many centuries earlier by Alexander of Aphrodisias. (1) 
The Ethics is proof that Spinoza was not a sceptical materialist. He was scorned and hailed as an atheist for generations, even though he clearly stated that nothing exists in the universe but God. His “naturalist metaphysics” is not the easiest subject to comprehend. Varying contemporary interpretations are in evidence. (2) The diversity in this respect is notorious. “There seem to be as many Spinozas as there are audiences seeking to appropriate him for their philosophical, political, or religious ends” (Nadler 2014:2). Caution is evidently required. 

In philosophy Spinoza is said to be a Cartesian, a Hobbesian, a Platonist, an Aristotelian, a Stoic, and a Machiavellian, among other persuasions. He is also a socialist, a Zionist, an anarchist, a Jeffersonian republican, the source of the Radical Enlightenment, and so on. (Nadler 2014:2) 

Spinoza was early identified with Kabbalism, as found in two books by Johann G. Wachter dating to 1699 and 1706. (3) More recent commentators prefer Maimonides as a point of orientation, while some affinities have been charted with other medieval Jewish authors like Hasdai Crescas (Manekin 2014). Both Crescas (4) and Spinoza were determinists. Spinoza did not accept freewill, rejecting beliefs in divine reward and punishment.
The Ethics is not a Kabbalistic text, exhibiting the framework of a mathematical treatise, conveying a strong rationalist complexion to the argument. Nevertheless, there are very substantial differences from Descartes, with whom the Neo-Cartesian  author is so often associated. 
Spinoza radically altered the Cartesian perspective by rejecting the three-substance view. (5) There is only one substance in the Spinozan universe; everything is God. His well known phrase “God, or Nature” (Deus, sive Natura) is easily subject to misreadings.
Spinoza was averse to anthropomorphism, avoiding what he considered to be superstitions. (6) He did not believe in miracles. (7) Spinoza was in reaction to the Calvinist preachers who routinely invoked “the will of God” and related clauses as a judgment against heretics. His exposition avoided creationism. Human beings are caught in a system of cause and effect that is independent of any divine providence.

The Ethics is an ambitious and multifaceted work…. Despite a dearth of explicit references to past thinkers, the book exhibits enormous erudition. Spinoza’s knowledge of classical, medieval, Renaissance, and modern authors – pagan, Christian, and Jewish – is evident throughout. Plato, Aristotle, the Stoics, Maimonides, Bacon, Descartes, and Hobbes (among others) all belong to the intellectual background of this work. At the same time, it is one of the most radically original treatises in the history of philosophy. It is also one of the most difficult. (8) 

Tracking the influences upon Spinoza is relevant. His account of the world “is possibly the strongest statement of pantheism of the time with no sign of mystical overtones” (Popkin:81). His pantheism emerges as an x factor. Pantheism is an eighteenth century word, referring to a doctrine in which God is identified with nature. Spinoza is known to have read mystical versions of pantheism available in his time. According to the late Richard H. Popkin, this means three possible sources of pantheism, one of these being a confirmed influence upon Spinoza.
Firstly, the sixteenth century poet Leone Ebreo (d.1523), a Spanish Jew whose Dialoghi di Amore is described as Neoplatonist. Ebreo (Abrabanel) gave expression to “two of Spinoza’s great goals in intellectual life: that of seeing the world in the aspect of eternity and that of achieving the intellectual love of God.” (9)
Secondly, the tragic figure of Giordano Bruno (d.1600), who was burned at the stake by the Inquisition. Bruno is strongly associated with Hermetic lore, a factor in Renaissance thought which was opposed by Marin Mersenne, a Catholic churchman and the major correspondent of Descartes. Spinoza was not a Hermetic enthusiast, but he may well have been sympathetic to the fate of a heretic.
Thirdly, Spinoza “may have been attracted to the philosophical kabbalism of Herrera or at least was willing to use something of it without taking anything from what he regarded as the lunatic fringe of kabbalism.” (10) This possibility is associated with the strong transition in the Ethics to what Spinoza called the third kind of knowledge, meaning intuitive apprehension (scientia intuitiva). In contrast, the first and second kinds of knowledge are sensory experience (or imagination) and reason.
Some writers affirm that Spinozan “intuitive” knowledge is something deductive or reductive. This is not conclusive evidence. Spinoza says: “From this kind of [intuitive] knowledge there arises the greatest satisfaction of mind there can be, that is, joy” (Curley 1996:175). He also supplies the consideration: “How much more powerful it [intuitive knowledge] is than the universal knowledge I have called knowledge of the second kind” (ibid:177). What perishes with the body is the first kind of knowledge, which “is of no moment in relation to what remains” (ibid:178). This is why cultivation of the second and third kinds of knowledge is so important, transcending the sensory world and resisting disintegration. 
Spinoza means that the sensory imagination does not remain after death, whereas the refined mind does endure. This factor is related to his theme that the affects (i.e., affections of the body) and emotions can be controlled by the mind, or “power of the intellect.”
On the basis of the first two kinds of knowledge, Spinoza might appear to be an exceptional Cartesian, or alternatively, a logical panpsychist. However, he was evidently aiming at something that is not found in the Cartesian repertory. He also did not agree with the Kabbalah occultists. “Spinoza really objected to the people who were finding all sorts of divine clues in the numerology, typography, and diacritical signs in the biblical text” (Popkin 2004:82). These fantasies were distractions from the third kind of knowledge, which has been interpreted in terms of “the culmination of the human quest for understanding that is only reached at the end of one’s philosophical journey, the intellectual love of God” (ibid:96).
The pedigree of amor Dei intellectualis is complex. The phrase is elevated in Ethics Part Five, being shown to derive from the treatment by Maimonides in his Guide for the Perplexed. The terminology involved has been traced to the sequence of Al-Farabi, Ibn Sina, Maimonides, Gersonides, and thus to Spinoza, who is credited with making the strongest effort to endow this concept with philosophical clarity (Harvey 2014). The theme of an intellectual passion goes back even earlier, and is associated with Aristotle.
Platonist influences have been invoked via scientia intuitiva. This means Plotinus, Renaissance Platonists like Ficino and Ebreo, and the eclectic Herrera. Spinoza owned a Spanish version of Ebreo’s Dialoghi, and he attended Talmud school in the same synagogue frequented by Herrera. The accusation is made that diverse interpretations of Spinoza’s “naturalised” philosophy have failed to understand Platonist elements, which were so pervasively influential in his day (Zovko PDF:1-2). 
Although Spinoza was strongly pitched against orthodox religious dogma, he was nothing of a sceptic. His outlook was “possibly the furthest removed from scepticism of any of the new philosophies of the seventeenth century.” (11) 
Spinoza did not finish the Ethics until 1675. In the early 1660s, he was visited at Rijnsburg by Henry Oldenburg, subsequently the prestigious Secretary of the Royal Society. Their correspondence continued until the end of Spinoza’s life. Oldenburg became resentful that the Jewish thinker rejected Christian beliefs involving supernatural events. Spinoza did respect Jesus, without viewing him in the conventional religious manner. (12)
The wealthy patron of Oldenburg was Sir Robert Boyle (d.1691), a chemist considered to be one of the greatest scientists in Britain. Oldenburg was eager to put Spinoza in epistolary contact with Boyle. This arrangement did not work as he had imagined. Five letters between Boyle and Spinoza, with Oldenburg as intermediary, give indication of strong differences. Oldenburg sent Spinoza a copy of Boyle’s Physiological Essays (1661). Spinoza responded by strongly criticising Boyle’s interpretation of his experiments on fluidity and firmness, and on nitre. This has been considered impertinent by empiricists and critics. However, “we ought to look afresh at Spinoza’s insistence on the epistemological insufficiencies of the experimental way.” (13) 
Spinoza was not an empiricist in the manner of Descartes. He did not trust the increasing vogue for experiments, even though he did take an interest in what was occurring in different countries. He possessed some scientific ballast in his familiarity with lenses and microscopes, components of which he made and assembled as a type of artisan. Spinoza had grasped that experiments did not always prove what the experimenters claimed. His attitude tended to be very dismissive. Spinoza made a pointed criticism (in his correspondence with Oldenburg) of Francis Bacon, whose inductionism was here considered to be lacking in rational depth.
Unlike Descartes, Spinoza was not a vivisectionist. Boyle was an advocate of vivisection, a practice favoured within the Royal Society. Nevertheless, Spinoza’s view about animals is not satisfactory. An argument is available in Sharp 2011. Many other commentators provide only brief remarks. “Spinoza, contrary to Descartes, sees the modal complex that constitutes a being as both physical and mental” (Popkin 2004:96).” A significant factor needs attention: “Spinoza is, of course, a panpsychist – for him each thing is animate to some degree” (Della Rocca 1996:194).
Spinoza reflected that sentience is not unique to humans. “After we know the origin of the mind, we cannot in any way doubt that the lower animals feel things” (Ethics 3p57s). However, he has been criticised for stating: “The law against killing animals is based more on empty superstition and unmanly compassion than sound reason” (Ethics 4p37s1). The related tenet of using animals “at our pleasure” is not the most ethical. One analysis of this drawback concludes that the argument is valid, while relying heavily on premises that most would be likely to reject (Grey 2013:380). A flaw in Spinozan reasoning is evident.
Overall, there are some discrepancies, ambiguities, and obscurities evident in the Ethics. A well known criticism is that Spinoza, in contrast to Maimonides, elevated self-esteem as the consequence of employing reason, relegating the humility emphasised by the predecessor (Ethics 4p52 and p53). The context relates to his observation that “the mob is terrifying,” therefore the prophets recommended humility and other religious traits for non-philosophers (4p54s).
A different kind of work is the Tractatus Theologico-Politicus (1670), defending freedom of speech and belief. (14) This treatise infuriated the Dutch Reformed Church, meaning the Calvinists. Opponents regarded the Tractatus as “a book forged in hell.” Contemporary analysis reveals this text as being the first to argue that intrinsic religion is independent of theology and liturgical rites, and that religious leaders should not be governors of a modern state (Nadler 2011).
The campaign launched against Spinoza was never systematic enough to achieve total suppression. This development was nevertheless “sufficiently effective to compel Spinoza to adopt the furtive methods of a more or less clandestine author” (Israel 1996:4-5). The Ethics was completed in this oppressive situation, but not published. 
In November 1676, Leibniz visited The Hague, there discussing philosophy with Spinoza on several occasions. Leibniz was shown the unpublished manuscript of Ethics (or parts of this). “Although there is no written record of their conversation, it seems likely that these discussions were among the most rewarding in the whole history of philosophy.” (15) However, Spinoza was apparently at first suspicious of motivation in this case. “The worldly Leibniz was the court intellectual par excellence” (Nadler 1999:341). By comparison, Spinoza was a retiring and independent philosopher with no inclination to a celebrity vocation.
A note by Leibniz relays what he was told about Spinoza by the German mathematician Tschirnhaus, a personal contact of the Jewish philosopher. This note includes the information: 

He [Spinoza] thinks that we will forget most things when we die and retain only those things that we know with the kind of knowledge he calls intuitive, of which only a few are conscious…. He believes [in] a sort of Pythagorical transmigration, namely that minds go from body to body. He says that Christ is the very best philosopher. (16) 

This reference indicates that Spinoza believed in a form of reincarnation. We have no further details of his very obscure outlook in that respect. Transmigration was a Neoplatonist doctrine, and also a theme of Kabbalists in the vocabulary of gilgul. However, there were different versions of gilgul, with many popular superstitions attaching. Spinoza is more generally associated with a “parallelism” of the mind and body. In Ethics Part 2, the mind appears to be inseparable from the body, but Part 5 conveys a different perspective. Spinoza affirms: “The human mind cannot be absolutely destroyed with the body, but something of it remains which is eternal” (Ethics 5p23). Recent commentators have remarked: 

The extent to which the mind is eternal seems to depend on what the human mind does during its embodied existence. The more one knows intuitively, the greater is the eternal part of one’s mind. (Koistinen and Viljanen 2009:22)

As to the significance of the meetings between Leibniz and Spinoza, there is no known sequel. Western philosophy was thereafter increasingly restricted to the academic circuit. The outlook was generally rather more confined than that of either the polymathic Leibniz or the pansychist Spinoza. 
(1)  Adler 2014. Alexander was a Peripatetic whose “views challenged the monotheistic tradition of belief in personal immortality” (ibid:15). Spinoza is thought to have been influenced by the Aristotelian theme, as mediated within the Jewish community of Amsterdam. The challenge is associated with the perspective of “God exists but only philosophically,” attributed to Spinoza and Juan de Prado in Christian sources. Cf. Popkin 2004: 23-4, 42-3, who queries the Nadler version, instead concluding that Spinoza was “moving in a more metaphysical direction” in his later years. Papers of the Spanish Inquisition depict Spinoza and Prado voicing, in 1659, the abovementioned affirmation of a philosophical God. See also Nadler 1999:135-8; Nadler 2011:7-12. Nadler 2002 argues that a crucial feature of Spinoza’s thought was his denial of personal immortality, here inferred as the reason for excommunication. Cf. the review by Martin Lin, who adds that other commentators, such as Alan Donagan and H. A. Wolfson, believed Spinoza to have a “robust notion” of personal immortality. 
(2) The suggestion has been made that Spinoza was an arrogant misogynist, and also a homosexual (Gullan-Whur 1998:142-3). The author of this theory composed a critical biography of Spinoza, advertised by a publisher in terms of: “This new approach demolishes the myth that Spinoza was a lofty ascetic.” A counter can be found in Shepherd 2005, chapter 35. An “ascetic” issue is involved here via Spinoza’s contention at the end of Ethics: “It is clear how much the wise man is capable of, and how much more powerful he is than one who is ignorant and is driven only by lust” (Curley 1996:180). Spinoza has been criticised by some writers for the controversial reference to women in his unfinished Political Treatise. Cf. the lenient tone in Gatens 2009, a feminist work of considerable sophistication.
(3) Wachter was a Protestant theologian familiar with Kabbalah. In his first book he attacked Spinoza and the Kabbalah, later revising his hostile opinion in the Elucidarius Cabalisticus (1706). Wachter urged that Kabbalah influenced Spinoza (Brown 2006:244-5). Wachter’s second book is “a philosophically unconvincing interpretation of Spinozism,” based on firsthand knowledge of sources, though compromised by an intention to reconcile Spinozism with Christian doctrine (Vassanyi 2011:224-233). Leibniz soon after read Wachter’s second book and refuted Spinoza (ibid:233-240).
(4) See Harvey 1998. Hasdai Crescas (1340-1410/11) was a Spanish anti-Aristotelian whose philosophical work Or Hashem (The Light of the Lord) opposed formulations of Maimonides.
(5) Numerous commentators state that Spinoza was influenced by Descartes. Some terminology does converge. However, in terms of ideation, there are pronounced differences. Spinoza early composed a reworking of the Principles of Philosophy by Descartes, an incomplete version which “does not reflect the format of the original” (Gabbey 1996:155). This discrepancy is viewed as an indication of Spinoza’s dissatisfaction with the Cartesian format. In the subsequent Ethics, Spinoza goes far beyond Cartesian maxims. In that work, Spinoza refers to “the celebrated Descartes,” and says they both “believed that the mind has absolute power over its own actions” (Curley 1996:69). Nevertheless, the same passage disagrees with Descartes about the human affects. In this respect, Descartes “showed nothing but the cleverness of his understanding” (ibid). Spinoza also strongly criticises the theory of Descartes about the pineal gland (ibid:161-2).
(6) Spinoza complains that people often compare the power of God with the power of kings. He urges: “No one will be able to perceive rightly the things I maintain unless he takes great care not to confuse God’s power with the human power or right of kings” (Curley 1996:34).
(7)  A well known passage occurs in the Appendix to Part 1 of Ethics, where Spinoza is more direct about superstition and popular religion. “One who seeks the true causes of [ostensible] miracles, and is eager, like an educated man, to understand natural things, not to wonder at them, like a fool, is generally considered an impious heretic and denounced as such by those whom the people honour as interpreters” (Curley 1996:29).
(8) Nadler 1999:226, referring to the “Euclidean architecture of definitions, axioms, postulates, propositions, scholia, and corollaries” for which the Ethics is famous. The geometrical method is daunting for those unacquainted with the format. This has nevertheless been argued in terms of an advantage, bearing “an intimate relationship to the content of Spinoza’s metaphysics and epistemology” (ibid).
(9)  Popkin 2004:18. Spinoza made much of “the intellectual love of God,” especially evocative in one of his scholia found in Ethics: “From this we clearly understand wherein our salvation, or blessedness, or freedom, consists, namely, in a constant and eternal love of God, or in God’s love for men” (Curley 1996:176). Some writers continue to portray Spinoza as an atheist.
(10)  Popkin 2004:81, referring to the pantheism arising from the Luria school, which became known in Amsterdam through the medium of Abraham Cohen Herrera (d.1635). In the Ethics, Spinoza is seen to have employed some terminology from Herrera’s Kabbalistic work Puerta del Cielo (ibid:19,81). Popkin also suggests that a further possible influence was Jacob Boehme, whose mystical doctrine attracted much interest from seventeenth century intellectuals. However, there has been a stronger tendency to associate Spinoza with Kabbalistic influences. For a relevant investigation, see Harvey 2007, focusing upon the work of Moshe Idel, a leading scholar of Kabbalism. “Idel’s Spinoza is not a Kabbalist, but a Jewish philosopher influenced by the medieval Hebrew speculative tradition” (ibid:92). According to Harvey, the arguments of Idel “deserve to be considered seriously” (ibid). See also Idel 1988:20,67, in relation to amor Dei intellectualis.
(11)  Popkin 2004:95, affirming that Spinoza “started his system at the point that others were trying to attain after they overcame the skeptical menace.”
(12)  See Fraenkel 2012:213ff, referring to Spinoza’s philosophical reinterpretation of Christianity, and viewing his well known critique of religion and scripture as a secondary project.
(13)  Gabbey 1996:180. Spinoza evidently believed that sensory knowledge is unreliable, belonging to the imagination (meaning his first kind of knowledge). Whereas the knowledge of causes is the domain of intellect (ibid:177). One pro-Boyle reflection is expressed in terms of: “Few of Spinoza’s specific scientific conclusions, either deductively or experimentally derived, are thought to be of scientific interest” (Gullan-Whur 1998:117).
(14)  See Melamed and Rosenthal 2010. The editorial introduction warns that the Tractatus is a difficult book for the modern reader, especially the philosopher. Spinoza here discusses at length historical and Biblical matters. He was writing for savants, not the general public.
(15)  Jolley 2005:18. Cf. Nadler 1999:340-342, who says: “Their long discussions covered a variety of important philosophical, political, and scientific topics, including the problems inherent in Descartes’s laws of motion and recent events in the Dutch Republic.” Cf. Antognazza 2009:168-9, 177-178, observing that by January 1675, Tschirnhaus had met Spinoza at least once, their contact continuing through correspondence. Leibniz had previously read and disapproved of some parts of the Tractatus. Leibniz “would continue to respect him [Spinoza] as a person even as he disagreed with him as a philosopher” (ibid:168). A year after their meetings, Leibniz wrote in a letter that the metaphysics of Spinoza was “strange and full of paradoxes” (ibid:178).
(16)  Klever 1996:46-47. Baron Ehrenfried Walther von Tschirnhaus was a Cartesian, described by Klever as one of the best friends of Spinoza. “Tschirnhaus credits Spinoza – and this is completely new in comparison with other sources – with a kind of Pythagoreanism, implying that souls in a certain sense transmigrate from one form of matter to another” (ibid:47). Professor Klever adds: “It is likely that the comparison with Pythagoras’s transmigration theory originates from Spinoza himself” (ibid).


Adler, Jacob, “Mortality of the soul from Alexander of Aphrodisias to Spinoza” (13-35) in S. Nadler, ed., Spinoza and Medieval Jewish Philosophy (Cambridge University Press, 2014).
Antognazza, Maria Rosa, Leibniz: An Intellectual Biography (Cambridge University Press, 2009).
Brown, Stuart, and Fox, N. J., Historical Dictionary of Leibniz’s Philosophy (Lanham, Maryland: Scarecrow Press, 2006).
Curley, Edwin, trans., Ethics (London: Penguin, 1996).
Della Rocca, Michael, “Spinoza’s metaphysical psychology” (192-266) in Don Garrett, ed., The Cambridge Companion to Spinoza (Cambridge University Press, 1996).
Fraenkel, Carlos, Philosophical Religions from Plato to Spinoza: Reason, Religion, and Autonomy (New York: Cambridge University Press, 2012).
Gabbey, Alan, “Spinoza’s natural science and methodology” (142-191) in Don Garrett, ed., The Cambridge Companion to Spinoza (Cambridge University Press, 1996).
Gatens, Moira, ed., Feminist Interpretations of Benedict Spinoza (Pennsylvania State University Press, 2009).
Grey, John, “Use Them at Our Pleasure: Spinoza on Animal Ethics,” History of Philosophy Quarterly (2013) 30(4):367-388.
Gullan-Whur, Margaret, Within Reason: A Life of Spinoza (London: Jonathan Cape, 1998).
Harvey, Warren Zev, Physics and Metaphysics in Hasdai Crescas (Amsterdam: J. C. Gieben, 1998).
——— “Idel on Spinoza,” Journal for the Study of Religions and Ideologies (2007) 6 (18):88-94.
——— “Ishq, hesheq, and amor Dei intellectualis” (96-107) in S. Nadler, ed., Spinoza and Medieval Jewish Philosophy (Cambridge University Press, 2014).
Idel, Moshe, Studies in Ecstatic Kabbalah (State University of New York Press, 1988).
Israel, Jonathan, “The Banning of Spinoza’s Works in the Dutch Republic (1670-1678)” (3-14) in W. V. Bunge and W. Klever, eds., Disguised and Overt Spinozism Around 1700 (Leiden: E. J. Brill, 1996).
Jolley, Nicholas, Leibniz (New York: Routledge, 2005).
Klever, W. N. A., “Spinoza’s life and works” in Don Garrett, ed., The Cambridge Companion to Spinoza (Cambridge University Press, 1996).
Koistinen, Olli, and Viljanen, Valtteri, “Introduction” (1-25) in Koistinen, ed., The Cambridge Companion to Spinoza’s Ethics (Cambridge University Press, 2009).
Manekin, Charles, “Spinoza and the determinist tradition in medieval Jewish philosophy” (36-58) in S. Nadler, ed., Spinoza and Medieval Jewish Philosophy (Cambridge University Press, 2014).
Melamed, Yitzhak Y., and Rosenthal, M. A., eds., Spinoza’s Theological-Political Treatise: A Critical Guide (Cambridge University Press, 2010).
Nadler, Steven, Spinoza: A Life (Cambridge University Press, 1999).
——–Spinoza’s Heresy: Immortality and the Jewish Mind (Oxford University Press, 2002).
——–A Book Forged in Hell: Spinoza’s Scandalous Treatise and the Birth of the Secular Age (Princeton University Press, 2011).
Popkin, Richard H., Spinoza (Oxford: Oneworld, 2004).
Sharp, Hasana, “Animal Affects: Spinoza and the Frontiers of the Human” in Journal for Critical Animal Studies (2011) Vol. 9 Issue 1/2. Online PDF.
Shepherd, Kevin R. D., Pointed Observations: Critical Reflections of a Citizen Philosopher on Contemporary Pseudomysticism, Alternative Therapy, David Hume, Spinoza, and Other Subjects (Dorchester: Citizen Initiative, 2005).
Vassanyi, Miklos, Anima Mundi: The Rise of the World Soul Theory in Modern German Philosophy (Springer: Dordrecht, 2011).
Zovko, Marie-Elise, Understanding Geometric Method: Hypothetical Dialectic in Proclus, Abraham Cohen Herrera and Baruch D. Spinoza (online PDF).

Kevin R. D. Shepherd

ENTRY no. 64

Copyright © 2015 Kevin R. D. Shepherd. All Rights Reserved.

Descartes and Vivisection

By Empiricism, Jesuit Theologians, Robert Boyle, Royal Society, Vesalius

Rene Descartes

Rene Descartes (1596-1650) opposed the traditional Scholastic philosophy of the universities, which at that time harboured an approach rooted in Aristotelianism as interpreted by the Christian Schoolmen. The Scholastics tended to identify their version of Aristotle with the Bible, maintaining that support for their exegesis could be found in Biblical text. Any refutation of Aristotle was thereby considered equivalent to blasphemy.
Descartes was born at La Haye, near Poitiers. His father was one of the French landed gentry, in a social situation where the clergy held prodigious political power alongside royalty. Descartes studied law at the University of Poitiers, gaining a degree. However, he did not pursue the career of a lawyer. After leaving military service, he lived a retiring existence in Holland, at places including Amsterdam and Leiden.
His major correspondent was Marin Mersenne (1588-1648), a theologian in contact with scientists and philosophers throughout Europe. Mersenne was a basic source of news for Descartes. The philosopher at first tended to take mathematics as the model for knowledge, an avenue demonstrated in his Rules for the Direction of the Mind. However, his basic field of endeavour is sometimes described in terms of natural philosophy, a subject contrasting with theology. Descartes developed a version of cosmology, employing a mechanistic physics.
In 1637, he published in French three scientific essays on optics, geometry, and meteorology. He was bypassing scholastic Latin. He did the same with his Discourse on Method, in which he elevated the “light of reason,” credited with the ability to distinguish between truth and falsity. That Discourse also emphasised a major difference between animals and humans; the distinction has since become a major source of disagreement. Descartes assumed an absence of mind in animals, comparing them to clock mechanisms.
In 1641, he published in Latin his Meditations on the First Philosophy. This became his most famous work. That book aroused objections from leading scholars and theologians. The author was basically in friction with Scholastic philosophy. His opponents included Calvinists. He was also in conflict with the trend of scepticism represented by Montaigne.
In 1644 appeared his Latin work Principia Philosophiae (Principles of Philosophy). This restates his version of metaphysics and also mechanistic physics. Descartes was in conflict with the Jesuit theologians or Late Scholastics, for example, Francisco Suarez. He was effectively pitched against Aristotle and Thomas Aquinas. In 1648, the curators of Leiden University confirmed their decision that only Aristotelian philosophy could be taught in their precincts. Professors in that establishment were forbidden to mention the name of Descartes.
The commentator has to be fair to the subject while observing his defects. Descartes was a mechanist who believed that he had evolved a perfect rationalism. This can be strongly queried, especially in view of the crude empiricism that emerges in the record of his activities. 
He even arranged [in 1646] for the slaughter of a pregnant cow so that he could examine the foetus at an early stage of its development. (Clarke 2006:332) 
Such actions were part of his insensitive approach to the issue of animal consciousness, encapsulated to some extent by his notorious theme that “animals are machines.” Descartes has been described as a pioneer of vivisection; he was by no means the only one. 
In 1646, an English royalist, namely William Cavendish (Duke of Newcastle), sent a letter to Descartes about the apparent ability of animals to think. The recipient made what appears to have been a reluctant concession. However, this occurred during his final years; the concession did not alter his basic standpoint. “This seems to me a very strong argument to prove that the reason animals do not speak is that they have no thought” (Clarke 2006:336). The reply of Descartes also included the reflection:
Though the animals do not perform any action which shows that they think, still, since the organs  of their body are not very different from ours, it may be conjectured that there is attached to those [animal] organs some thoughts such as we experience in ourselves, but of a very much less perfect kind. (Kenny translation, 1970)
The earlier letter of Descartes to Plempius, in February 1638, affords proof that he practised vivisection (Cottingham 1991:79-85). Descartes here described his vivisection of a living rabbit. Descartes also “wrote in correspondence that the mechanical understanding of animals absolved people of any guilt for killing and eating animals” (Animal Consciousness). His category of belief was very convenient for vivisectionists. The followers of Descartes, meaning Cartesians, are now criticised as the brutal precursors of widespread laboratory practice, which continues to masquerade as a perfect empirical science confounding the subject of animal ethics
Jesuits at this period may also have practised vivisection; certain references have been debated. A systematic approach to the theories of Descartes, on the part of his posthumous followers, led to the explicit support of vivisection. A case in point being Nicolas Malebranche (1638-1715), an influential neo-Cartesian mechanist who argued, on religious grounds, that animals lacked a soul and were incapable of pain or suffering, therefore being beyond any moral consideration. Some commentators express uncertainty as to whether Descartes himself believed this (Boden 2006:72). The fact is that Descartes performed animal experiments, to an unknown extent, and clearly believed that reference to vivisection was legitimate. 
Descartes ascribed sentience to animals. However, in contrast to Aristotelians, he explained sentience in mechanistic terms, eschewing concepts of a “sensitive” soul (Boden 2006:72). In his Discourse on Method (1637), Descartes stated that the divine gift of the soul distinguished humans from animals. Scientists found, in his writings, a reason to discount the behavioural response of animals to vivisection (Monamy 2009:10-11). 
A generally received idea is that Descartes followed no tradition, being committed to accept only what he learned firsthand. He was actually following the tradition of Vesalius in relation to dissection. The successors of Vesalius at Padua University had engaged in vivisection; the Fabrica of Vesalius has been shown to include this favoured practice. Descartes was also in support of conventional Christian doctrines about salvation of the soul, in which animals were not celebrated. His mechanist version of the universe was later proved erroneous. His physics transpired to be inadequate. A major anatomical theory of Descartes came under criticism: 

Descartes tried to explain most of our mental life in terms of processes involving the pineal gland, but the details remained unclear, even in his own eyes. (Stanford Encyclopedia

In 1629 he relocated to Amsterdam, then a new centre of anatomy, a fashionable Renaissance subject which he embraced. Descartes lived for a period in the Kalverstraat quarter, inhabited by butchers. He regularly visited the butcher stalls. While reading the works of Vesalius, he would purchase animal carcases, carrying these back to his flat for dissection. In a letter of 1639, after moving to other places, Descartes told Mersenne that he had spent much time in dissection for eleven years (Sawday 1995:147ff; McCance 2013:48-9). Such activities are questionable in the pursuit of a viable philosophy, despite the associations of a scientific revolution. Descartes was basically an empiricist, gaining disproportionate fame as a deductivist. The combination of tendencies proved a source of confusion. 
In 1632, Descartes wrote to Mersenne: “I am now dissecting the heads of various animals, so that I can explain what imagination, memory, etc. consist in” (Gaukroger 2000). His bland assumption, in respect of explanation, may be regarded as imaginative rather than anything more comprehensive. 
Descartes was preoccupied with both human and animal corpses, accomplishing “many post-mortem dissections.” He frequently visited abattoirs and the gallows (criminals were dissected after hanging). Not knowing where to stop, he followed the example of William Harvey (1578-1657) in vivisecting a few animals: fishes, eels, and a hare (Boden 2006:61). He describes the vivisection of a dog in his Description of the Human Body and of All Its Functions. Descartes does not there say that he performed the operation. However, some commentators have very feasibly construed that he did. Arguing against Harvey, the empiricist Descartes  affirms: “If you slice off the pointed end of the heart in a live dog, and insert a finger into one of the cavities…” (Cottingham 1985:317). The passage can easily offend dog lovers.
“There is no point in denying that Descartes’ vivisection and ill-treatment of animals is disgraceful” (Grayling 2006:159). The issue does not stop there. 
According to Richard Dawkins, Descartes “stood in a long tradition of vivisectionists including Galen and Vesalius, and he was followed by William Harvey and many others” (On Vivisection). His inspirer Vesalius was enthusiastic about the dissection of human corpses and animal vivisection. Vesalius (1514-64) authored the influential De humani corporis fabrica (1543). The word vivisection was not invented until 1702. The earlier word dissection can be equivocal in context.
Certain classical reports are alarming. The ancient Greek practitioners Herophilus and Erasistratus dissected (or vivisected) living human beings at Ptolemaic Alexandria. The sources are Aulus Cornelius Celsus (d.c. 50 AC) and Tertullian. The medic Herophilus (circa 320-260 BC) reputedly dissected at least 600 live prisoners, an operation endorsed by a monarch. The details have been disputed. In some directions, deniers of the sources are considered apologists for classicism. In his De Medicina, the Roman scholar Celsus affirms that Herophilus and his assistant “laid open living criminals” (Staden 1989:52). Herophilus influenced the “Empiricist” school of medicine, as distinguished from the “Rationalist” school of Hippocrates (ibid:50). Animal vivisection was a prevalent practice by the time of Galen (second century AC). 
As a philosopher, Descartes surely ought to have been more resistant to fashionable cruelty of the leisured class of scientists active in his own time. His inclination to the contrary places him in the same category as reprehensible events of the 1660s, when thirty vivisections were conducted in the presence of assembled members of the Royal Society in London. 
A well known early report of brutal Cartesian vivisectionists at the Port Royal School, in Paris, has aroused differences of interpretation. One commentary says the report “may not be trustworthy.” That account was written years after the events described. However, there are other reports of animal experiments in the late seventeenth century, along with implications that Cartesian mechanists made no attempt to minimise animal suffering, believing that this was an illusion (Boden 2006:72-3). 
The Port Royal report describes dogs being nailed alive to boards for dissection. This was during the 1650s. The callous behaviour is very easy to credit, as the Jansenist milieu under discussion is known to have been influenced by Cartesian attitudes, via leading figures at the Port Royal School and related Abbey. Someone had taught the pupils a Cartesian approach to supposed automata. The report was included in the Memoires of Nicolas Fontaine (1625-1709), a contribution which is very difficult to ignore (on the Port Royal School, see Delforges 1985).
Vivisection increased substantially as a consequence of Cartesian doctrine, being avidly practised by the Royal Society. This organisation was founded by a group of scientists including Robert Boyle (1627-91) and Robert Hooke (1635-1703). Their crimes are on record, including the injection of poisons, ever since a favoured device of  laboratory personnel. Dogs, sheep, and other animals were the victims. Hooke is known to have vivisected a dog in 1667, and in this respect was a virtual blood brother of Descartes.
Hooke’s prestigious colleague Robert Boyle was an ardent defender of vivisection, viewing critics as sentimentalists. How tough and supremely insensitive the empiricists were. The objectors were here viewed as “a discouraging impediment to the empire of man over the inferior creatures of God” (Boden 2006:73). 
The empire of man, considered so desirable by Boyle, was strongly convergent with developing inclinations for a colonial British Empire. The successors of the Romans (and the abominations of Galen) were eager to assert their scientific superiority over the supposed barbarians in the East (plus Africa and the Americas). The superiority and invasions can be strongly questioned. The mechanist use of brute force is no proof of cultural perfection. 
Boyle was a hero of the empiricist philosopher John Locke (1632-1704). The vivisectionist outlook evidently did influence Locke to some extent. An episode is reported, dating to the 1650s, of how he skinned a frog to prove circulation of blood. Though a mere scratch compared to agonies devised by the Royal Society, this detail is not attractive. Subsequently however, Locke recognised that animals could feel, moreover, that cruelty toward them is morally wrong. In Some Thoughts Concerning Education (1693), he advised that children should be reared to detest the mistreatment of animals, as a means to prevent cruelty against humans.
In this respect, Locke surpassed Spinoza, who recognised that animals feel, while remarking in Ethics that animals could be used as humans pleased. Locke can be compared to Aquinas, who much earlier concluded that cruelty to animals was evil, potentially leading to human victims. In the early years of Locke, the Puritans frowned upon blood sports in England, a mercy ending when Charles II re-established monarchical power.
A century after Boyle, the essayist Samuel Johnson (d.1784) complained about the “arts of torture” practised by some medical men, whose favoured pastime was “to nail dogs to tables and open them alive” (Boden 2006:73). Johnson was an opponent of slavery and a lover of cats. Elite members of the Royal Society continued experiments on live frogs, dogs, and horses. In more humane channels, the English gained a contradictory reputation as horse lovers. The clergyman Stephen Hales (1677-1761) was a partisan of Newtonian science at Cambridge. In 1714 he conducted dubious experiments on horses and dogs. Hales was elected a Fellow of the approving Royal Society in 1718. He afterwards turned his attention to plants and philanthropy. However, he continued to be praised for bleeding a sheep to death while measuring heartbeat. 

Not until the 1870s was official action taken to limit disturbing laboratory practices. The substantial continuation was not considered satisfactory by the National Anti-Vivisection Society, founded in that same decade. 
Boden, Margaret A., Mind as Machine: A History of Cognitive Science Vol. 1 (Oxford University Press, 2006).
Clarke, Desmond M., Descartes: A Biography (Cambridge University Press, 2006).
Cottingham, John, et al, trans., The Philosophical Writings of Descartes (3 vols, Cambridge University Press, 1985-91).
Delforges, Frederic, Les Petites Ecoles de Port-Royal, 1637-1660 (Paris: Cerf, 1985).
Gaukroger, Stephen, et al, eds., Descartes’ Natural Philosophy (Abingdon: Routledge, 2000)
Grayling, A. C., Descartes (2005; London: Simon and Schuster, 2006).
Kenny, Anthony, trans., Descartes: Philosophical Letters (Oxford University Press, 1970).
McCance, Dawn, Critical Animal Studies: An Introduction (Albany: State University of New York Press, 2013).
Monamy, Vaughan, Experimentation: A Guide to the Issues (2000; second edn, Cambridge University Press, 2009).
Sawday, Jonathan, The Body Emblazoned: Dissection and the Human Body in Renaissance Culture (Abingdon: Routledge, 1995).
Shepherd, Kevin R. D., web article Rene Descartes Philosopher and Scientist (bibliography). 
Staden, Heinrich von, Herophilus: The Art of Medicine in Early Alexandria – Edition, translation, and essays (Cambridge University Press, 1989).
Kevin R. D. Shepherd 
February 2015, modified 2021

ENTRY no. 63 

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