It is often forgotten that Descartes conceived of himself as a physician as much as a rationalist philosopher. Descartes claimed that improving human health ‘has been at all times the principal goal of my studies’, and he vowed in the Discourse on the Method (1637) to dedicate himself to ‘no other occupation’ than freeing mankind from sickness ‘and perhaps also even from the debility of age’. Descartes conducted dietary experiments upon himself and concluded that meat was unsuited to the mechanism of the human body, whereas the vegetable diet could, in the words of his friend Sir Kenelm Digby, ‘lengthen out his life span to equal that of the Patriarchs’.
Like the mystical Rosicrucians he so admired, Descartes dispensed free medical advice throughout his career, and shared his secret about the efficacy of vegetables with other ‘friends of his character’. His companion the Abbé Claude Picot was so impressed that after spending three months at Descartes’ hermit-like retreat in Egmond, ‘he wanted to reduce himself to the institute of Mr Descartes, believing that this was the only way to make a success of the secret which he claimed our Philosopher had discovered, to make men live for four or five hundred years.’ When in 1650 Descartes died at the pitiful age of fifty-four, Picot – after all the claims he made for his diet – was understandably discomposed, and insisted that without a freak accident ‘it would have been impossible’; others even suspected that Descartes had been poisoned.16
Descartes’ mechanistic physiology convinced him both that it was morally acceptable to eat meat and, simultaneously, that it was healthier not to. This reasoning placed him at the crossroads of the vegetarian debate of the eighteenth century. Ethical vegetarianism was built on a refutation of Descartes’ ‘beast-machine’; medical vegetarians used his mechanistic system of the body to explain the benefits of the vegetable diet. The fact that Descartes himself saw no contradiction between refusing one and embracing the other could be viewed as demonstrating the absolute distinction between the medical and ethical motives for vegetarianism – but that is not how some eighteenth-century doctors saw it. When they argued that the body’s hydraulic mechanism was clogged and damaged by meat, they almost invariably acknowledged that this implied that God never intended humans to eat animals.
Descartes’ diet ostensibly had nothing to do with ethical objections to killing animals. Indeed, his Discourse on the Method directed a specific attack against the cult of loving animals inaugurated by Michel de Montaigne’s Apology for Raymond Sebond (1585). Descartes’ dualist theory of the beast-machine seems to have been devised partly in order to extinguish these feelings of compassion. This is borne out by Descartes’ early manuscripts which show that he first devised the idea of the animal automata in 1619–20 after his friend and superior brother at the Jesuit college, Father Molitor, presented him with the animal-friendly Treatise on Wisdom (1601) by Montaigne’s disciple Pierre Charron.17
Following Descartes’ lead, Malebranche also attacked the ‘dangerous’ Montaigne for being ‘angry with Men; because they separate themselves from … Beasts, which he calls our Fellow Brethren, and our Companions’.18 Malebranche explained that sympathy was just a mechanical process in the body – like blood circulation, an animal function as bestial as a sexual urge – and should therefore be subjugated like other carnal appetites to the superior power of reason: and reason indicated that animals were not really feeling pain in any case.19 This lesson was lost on ‘Persons of a fine and delicate Constitution, who have a lively Imagination, and very soft tender Flesh’, especially women and children who, he said, ‘are Mechanically dispos’d to be very Pitiful and Compassionate’.20 But Malebranche recognised that even being as convinced as he and Descartes were that animals did not feel pain was no protection against this corporal feeling of sympathy. For this inescapable automatic compassion, he said, ‘often prevents those Persons from Butchering Beasts, who are the most convincingly perswaded they are meer Machines’. He warned that failing to realise that the body was sending misleading signals was ‘a prejudice that is very dangerous in view of its consequences’.21
Though tantalisingly unverifiable, it would be most surprising if Descartes’ medical decision to abstain from meat also made him feel better because it avoided the irrepressible sensation of sympathy for animal suffering. But by the end of the eighteenth century at least, that is precisely what some commentators believed was the case. One author even implied that it was because of his humanity that, ‘in imitation of the good natured Plutarch, [Descartes] always preferred fruits and vegetables to the bleeding flesh of animals.’22
Regardless of Descartes’ own feelings, it is superlatively ironic that this Cartesian mechanistic explanation of sympathy was turned into an argument for ethical vegetarianism in the eighteenth century. The fact that sympathy was an innate function of human anatomy convinced many that it was an embodiment of natural or divine law – especially since most people believed God had personally designed the human body. This came to underwrite the argument that sympathy was an innate source of moral and social principles, formulated by the ‘moral sense’ philosophers from the 3rd Earl of Shaftesbury (1671–1713) to Francis Hutcheson (1694–1746) and David Hume (1711–76), until it was finally revised by Immanuel Kant (1724– 1804).23 It became common to extrapolate the same argument onto sympathy for animals and for Jean-Jacques Rousseau this constituted a basis for animal rights. As the Dutch physician-philosopher Bernard Mandeville (1670–1733) expressed it in 1714, because sympathy ‘proceeds from a real Passion inherent in our Nature, it is sufficient to demonstrate that we are born with a Repugnancy to the killing, and consequently the eating of Animals’.24 At a time when natural observations carried as much force as biblical strictures, this deduction of natural law became one of the most potent arguments for vegetarianism. Anti-vegetarians fiercely responded by adopting the neo-Cartesian argument that sympathy should be subjugated to reason and to the scriptural permission to kill animals.
Even if Descartes was not one of those described by Malebranche, who knew animals were machines but still could not bring themselves to kill them, his extraordinary legacy influenced both sides of the medical and ethical vegetarian debate which flourished throughout the eighteenth century.
ELEVEN Tooth and Nail: Pierre Gassendi and the Human Appendix
In 1699 the anatomy lecturer at Surgeon’s Hall in London, Edward Tyson, made a breakthrough in the understanding of humanity’s relationship to beasts. For the first time in Western science, Tyson dissected the body of an ape, and to the fascination of all found that in nearly every way it resembled a human. He called it the ‘Orang-Outang’ – Malayan for ‘Man of the Woods’ – or in Latin, Homo sylvestris, and his specimen still stands in the upright posture of a human in the British Museum. The ‘Orang-Outang’ was in fact a young chimpanzee, but Tyson’s observations were nevertheless sensational and were still being consulted 150 years later when Charles Darwin (1809–82) devised his theory on the ‘missing link’.
Tyson’s