← History of Philosophy Without Any Gaps
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Hi, I'm Peter Adamson, and you're listening to the History of Philosophy podcast, brought to you with the support of the Philosophy Department at King's College London and the LMU in Munich. Online@historyoffphilosophy.net Today's episode this gland is your Cartesian Science the most obvious way to make a huge impact on science is to make discoveries. This is what we expect from scientists today, honoring their breakthroughs with Nobel Prizes and the like. But it isn't the only way. Though Aristotle did make some genuine discoveries, especially concerning animal anatomy, most of his scientific beliefs were false. He denied that light travels the thought the earth doesn't move, and that flies and worms generate spontaneously. One especially perplexing case is his claim that women have fewer teeth than men, which seems like it would have been easy for him to check. In fairness, it's been suggested that maybe he did check, and that ancient women often had missing teeth due to calcium deficiencies. Yet his various misconceptions did not stop him from becoming the most influential scientist who has ever lived, at least as measured by longevity. Nearly two millennia after Aristotle's death, his views still held sway, and resistance to them provoked cultural and institutional backlash. Of course, this long shelf life was not due to individual claims about teeth, light, worms, or even the motion of the earth. Aristotle's power lay in the paradigm he devised for doing science. It combined an empirical methodology with broadly applicable conceptual distinctions like potentiality versus actuality, matter versus form, and substance versus accident. What Aristotle provided was not individual discoveries, but a whole way of seeing the world. Though Descartes would not have appreciated the comparison, he was much like Aristotle in this respect. He made genuinely important discoveries in mathematics and also had scientific advances to his name. He was, for instance, the first to announce the sine law of refraction, though it had been discovered by Thomas Hariot decades earlier. But most of Descartes notable scientific proposals were wrong. His cosmology, with its swirling vortices, his corpuscular analysis of light, and his anatomy, which notoriously makes the pineal gland in the brain the seat of the soul and the body. We now know that its role is simply to produce melatonin, a hormone that regulates the sleep cycle. Rather an appropriate mistake for Descartes to have made actually, given his equally notorious inability to get out of bed early. Despite his low success rate as a scientist, his impact on science rivaled that of Aristotle for the better part of a century, and this for the same reason. Descartes offered a new set of methods for scientific inquiry and an appealing picture of the physical world. He made no use of those Aristotelian concepts like actuality and substantial form. Instead, for Descartes, all natural bodies are made from invisible corpuscles which come together to build more or less complex holes, which he compared to machines, the most complex organic machines being, of course, the bodies of animals and humans. While Descartes did contribute to a wide array of scientific fields, it was in the study of these living bodies that he had the biggest impact, which is exactly as he would have wanted it. In 1630, he stated with typical ambition that he wished to devise a medicine grounded on infallible demonstrations in a more modest frame of mind. Though he admitted to Mersenne only six years earlier that he had not yet discovered enough about medicine even to heal a fever. Still, he was confident that his mechanist corpuscularian approach would ultimately reveal the secrets of the human body. He was deeply committed to the practice of empirical science, which is why he carried out those dissections of animal body parts acquired from butchers. But his theories also made plenty of room for arguments from abstract principle, with his views on the pineal gland being a prime example. He argued that this small part of the brain was best suited to serve as the seat of the soul because it is simple, that is, without smaller structural parts, centrally located in the brain and capable of moving this way and that, so as to steer the flow of animal spirits. Descartes immediate followers built on both his methods and his concrete proposals. Henricus Regius wrote a treatise on natural philosophy in 1646, a few years before Descartes death, and it was praised by Massen and Huygens for expanding on what Descartes had written on anatomy. Already a few years before that, Regius had been described by one observer as a Cartesian physician. Befitting that title, he he defended Descartes positions on such topics as the pineal gland. Descartes feeling about Regius, though, was that with friends like this, he hardly needed enemies. I've already mentioned that Regius sparked the Voitius affair by polemicizing against the scholastics at Utrecht. And Regius also annoyed Descartes by adopting a reductionist position on the relation between mind and body. More faithful were Roh and La Forge, both of whom wrote on natural philosophy and anatomy. Like Descartes, they sought to combine empirical observation with reasoning based on fundamental principles. As Rouel put it, it is advantageous to mix experiments and arguments together. That balanced approach may come as a surprise, given that Descartes and his followers are typically assumed to have been rationalists, as opposed to the empiricists ascendant in early modern British philosophy, like Locke and Hume. But the Cartesians had a good reason to use observation in science. I've mentioned one of them in an earlier God in his omnipotence can set up the world however he sees fit. So first principles are only going to take us so far. We have to go look at the world to see which of the infinite possibilities God has chosen. This point was put very forcefully by Raoult. Since the world is the work of God, who could divide it into as many parts as he pleased and dispose them in an infinity of different ways, it is impossible to know their number and arrangement by any reason that can be taken from the nature of things. And it is only experience that can teach us what among the several ways that God can dispose them, which it is that he was pleased to choose. Yet even at the time, some thought that the Cartesians did depend too much on argument and not enough on experience. Henry Oldenburg, secretary of the Royal Society in England, complained that French natural philosophers are more discursive than active or experimental. If we look at Raoul's scientific practice, the situation turns out to be a bit more complicated. He was without doubt engaged in experimentation. For instance, when he used syringes and other vessels to test the possibility of creating a void, Rohault scornfully dismissed the idea that matter simply has a horror of the void or horror vacui and will rearrange itself to make sure that no space remains empty. This, he said, would be like saying that lumber gets transported to Paris because it is afraid of the cold. Like Descartes, and unlike his fellow Cartesian, Gerard des Cordemois, Rouault rejected the possibility of a vacuum. He tested this with a glass syringe, trying to retract the plunger when the entry hole was blocked. If the plunger can be pulled back, then void must be arising alongside the air in the syringe, since no new air is able to enter. When Raoult inconveniently found that the plunger could indeed be retracted, he concluded that there must be miniscule pores in the glass, allowing in additional air. This looks like fitting the empirical findings around a physical theory rather than the other way around. Notwithstanding such failures to embrace a fully empiricist method, the Cartesians liked to contrast themselves to the scholastics who did natural philosophy by reading Aristotle instead of doing experiments. Raoult dismissed their philosophy as a science of words rather than things. The bitter criticisms he and other Cartesians aimed at the schoolmen had to do with both method and institutional power. Since the late Middle Ages, the universities had exercised control over medical education in France. They taught theories of disease and the human body based on Aristotle, Galen, Avicenna and other authors of the classical and medieval periods. This approach gradually changed over the 17th century, though, with teaching organized around themes in physiology, pathology, semiology, hygiene and therapeutics, instead of just commenting on standard, authoritative texts. Still, Galenic approaches held sway in the French academic world until about 1680. Which is not to say that university medical scholars faced no opposition. For one thing, medical services were offered less by such scholars than by practitioners like informally trained healers, midwives, local surgeons and apothecaries. Attempts were made to regulate the situation from the top. The surgeons and apothecaries were trained in an apprentice system and organized into guilds like other trades. Especially after the wars of religion, which gave the French state a strong motivation to centralize their control over society, there was a trend towards institutionalization of medical therapies. There was also conflict and rivalry between the university doctors with their book learning and the medical practitioners who relied more on experience passed down across generations. Under Louis XIII and Louis xiv, this conflict was resolved in favor of the scholars. The premier royal physician was given oversight over all medical practitioners. Similarly, in 1536, a law prevented any physician from working in Paris without a license from the university. We can see here the roots of something that is entirely familiar to us today, a kind of credentialing and monitoring system that controls who is and is not allowed to offer medical services. Medical scholars in the traditional mode also experienced pushback from people who were more like their peers and who put forward theories that challenged the orthodoxy based on Aristotle and Galen. A key example would be the discovery of the circulatory system by William Harvey, announced in 1628. True to form, the Paris medical faculty debated this in 1642 and dismissed it since it was incompatible with Galen. Then there was the new system of chemistry and medicine associated with the name of Paracelsus, which already swept Europe in the 16th century. For a reminder, you can go Back to episode 388. Parisian doctors sometimes embraced the Paracelsian teachings, like the notion that one can cure a variety of illnesses with liquid gold. Under Cardinal Richelieu, such ideas even became popular at the French court. All this is relevant for the development of Cartesian medicine, and in a couple of ways. First, there was plenty of intellectual ferment within the medical scholarly community, meaning that Cartesianism was More like a new party to an ongoing debate, rather than a lone challenger to a solidly established and monolithic discipline. Second, the Cartesians needed to respond not just to the university masters, but also to less orthodox figures like Paracelsus and Harvey. Already, Descartes had to consider these questions. At Mersenne's instigation, he read the work of Harvey and decided he could welcome the new theory, since it fit well with his idea of the human body as a hydraulic mechanical system. Cartesian followers carried on his interest in the circulatory system, a striking example being Robert Desgab. He was curious about the possibility of carrying out blood transfusions. After all, if blood is just a fluid pumping around the body, then why can't we pump it from one body into another? He wrote on the topic in 1668, the same year that the first successful blood transfusion was supposedly carried out in France. A year later, an alarmed French parliament outlawed the practice. Des Gabet might have found that decision prudent, given the warnings he gave about the procedure. It was imperative that air not contact the blood and that care should be taken to match donor to recipient. That was a good intuition on his part, though of course neither he nor anyone else knew about blood groups. Yet he had in mind that the two people involved should have a similar mix of humors. When it came to the Paracelsins, Descartes was much less impressed. He obviously could not accept their view that all things have fundamental chemical constituents, namely mercury, sulfur and salt. Even if these substances are primary for the practical concerns of the chemistry, they are not truly primary. For Descartes, they would themselves be made of the still more basic matter that is nothing but extension. Thus he said about chemical elements that they are distinguished only by having parts of different shapes. His follower, Pierre Sergent Regius, likewise insisted that the supposed chemical principles have a first element underlying them, just like any other body. He did, however, allow that it might be, practically speaking, impossible to break down something like salt and into anything else. Again, we see here theory trumping practice. You don't identify the most fundamental matter in a laboratory. You do it in an armchair by reflecting on the nature of body itself. On the other hand, one might use empirical findings as hints to the shapes of the particles that make up the elements. This was the approach of Nicolas Lamery, who was called the Descartes of Chemistry. He suggested that acids must consist of pointed parts, which would explain why acid salts crystallize in sharp configurations. Alkalis, meanwhile, must be made of brittle parts full of holes, which is why acids can penetrate them and dissolve them. While that isn't wholly implausible, it also seems like mere guessing, a sense we also got from Descartes own ideas. In Natural philosophy and Medicine. A criticism of the movement that appeared in 1672 called Letter from a Philosopher to a Cartesian Friend mocks this sort of speculation. Content yourselves by saying that the pores are arranged in a certain manner, that they are of a certain shape, and that the parts that conform to certain openings pass through, and that others are stopped. You try to get away with a certain but if I ask you what this certain shape is, and what the certain manner, and what is this certain juice and these certain parts, you have nothing to say other than that you know no more. In a similar spirit, one author, writing in 1696, remarked that the elusive Cartesian matter is just like the prime matter of the Scholastics. Both are I know not what. Given this, why not follow the Scholastic theory, which at least has antiquity and tradition to recommend it? One of the most passionate critics was Pierre Daniel Houeth, who sarcastically called Regius the prince of the Cartesian philosophers, recognized in all the alley ways and among witty and accomplished ladies as the protector of subtle matter, patron of globules and defender of vortices. This was mere invective, of course, and invective laced with sexism at that. The reference to witty and accomplished ladies was a swipe at the popularity of Cartesianism among women intellectuals of the time. But Houillet made more principled objections too, especially that Cartesian science had fallen short of its pretensions to offer proofs grounded in clear and distinct ideas. To this, Regius simply replied that Houet was expecting too much. Natural philosophy is not a demonstrative science, but can only provide probable explanations, and Descartes explanations were the most probable ever devised. But that attitude of fidelity to Descartes was itself a problem. Leibniz complained that the Cartesians were a sect whose adherence to the Master's teachings prevented them from making further progress. A good test case for this proposition would be the infamous identification of the pineal gland as the meeting place of soul and body. This was subjected to a searching critique by Nicolas Stenno, an anatomist from Denmark. He was broadly sympathetic to the Cartesian project. You might remember me quoting his praise of Descartes back in episode 469. But that praise included a significant caveat that Descartes account of the brain is not found entirely conformable to experience. Steno knew what he was talking about having extensive experience with dissections, some of which he did as public demonstrations in Paris. His research, unveiled in A Discourse on the Anatomy of the Brain that appeared in 1669, showed that the pineal gland was entirely unsuitable to play the role Descartes ascribed to it. It was fixed in place, inflexible and unmoving, contrary to what Descartes had claimed. And it was not linked to the nervous system in the way one would expect for a commanding organ. To Steno's mind, this cast doubt on the whole Cartesian system. If they have erred to such a degree when it comes to material things that are laid before our senses, we what assurance can they give me that they are not equally mistaken when dealing with God and the soul? With Steno, we see a genuine commitment to using empirical observation as a check on philosophical speculation. Though he accepted the Cartesian claims that body is nothing but extension and that the mind is fundamentally different from the body, he remained agnostic about their interrelation. He noted that the same physical stimulus can produce many different reactions, giving the example of printed music, which might variously make a human sing, play an instrument or dance. From an empirical point of view, it remains mysterious why the sheet music elicits these different responses on different occasions. So such things are simply not susceptible to experiment. Many philosophers of science today would admire Steno's caution and praise his reliance on empirical data to critique theories that had ranged too far into speculative territory. And at the time, reactions were similarly positive. Louis Laforge, Descartes most stalwart defender, rebutted Steno with diagrams of the brain and a commentary that were included in an edition of Descartes Treatise on Man. But most other Cartesians quietly dropped the idea about the pineal gland, including Regis, who just chose a more promising part of the brain in its stead. The developments I've discussed so far in this episode were centered in France, but we see echoes in other parts of Europe. A Cartesian upholder of experimentalism in the Netherlands was Burchard de Volder, a professor of mathematics and natural philosophy in Leiden. He went to England and brought back ideas about experience based science, raising funds to build a physics theater at the university for a textbook he taught from Roh's Treatise on Physics. And like Raoult, he encouraged students to combine observation with principled arguments and based on clear and distinct ideas. Or take Johann Jakob Waldschmidt, who actually studied with Raoul and then taught at Marburg in Germany. He endorsed some of the Cartesian ideas we've seen already. Seizures are, he thought, caused by blockages to the pineal gland and chemical interactions are explained by the shape of the underlying particles. He even made the same point about alkalis being full of holes or pores and to explain why they can be dissolved. Nor were these far flung Cartesians content simply to repeat the ideas of the movement. A particularly interesting case is Theodore Kranen, who taught in Nijmegen and Leiden after studying at Duisberg under the Cartesian professor Johann Klauberg. Seeking an empirical proof for the theory of the pineal gland, Krahnnen hit upon the phenomenon of catalepsy, a state in which patients have paralyzed limbs but retain their awareness and mental life. This, he thought, could be explained only by saying that some part of the brain was being affected because the rest of the body, as verified by taking the pulse and monitoring rate of breath, seemed to be in good working order. Down in Italy, too, Descartes natural philosophy was taking root. The first to propagate his ideas was apparently Tommaso Cornelio, who was a professor at the University of Naples and and started engaging with the ideas of Descartes in the 1640s. This gives us our first glimpse of something we'll be seeing later in more detail, that Naples was a particularly important and vibrant intellectual center in the early modern period. Cornelio and others were, however, reluctant to accept the full mechanistic program of Cartesianism, feeling that there must be some kind of vital or organic power to explain the various functions carried out by the human body. While that may seem like a holdover of the doomed science found in Aristotle and Galen, it may rather be a sign of influence from more local and recent thinkers like Telesio and Campanella. Either way, we shouldn't condemn thinkers for being reluctant to jump on the Cartesian bandwagon. This movement achieved a lot, but mostly by critiquing long established scientific theories that did need to be abandoned. When the Cartesians tried to offer positive explanations of their own, they usually did no better than their scholastic opponents. I can't resist closing with an amusing example taken from the domain of embryology. Descartes was confronted with a supposed phenomenon in which something seen by a pregnant woman later appears on her baby as a birthmark with the same shape. This, he reasoned, could happen because images are passed from the mother's visual system to down to the womb through the vital spirits. Years later, there was a debate at one of the societies that attracted Cartesians over how to explain a stillborn infant that looked more like a monkey than a human. It turned out that in this case the mother had seen a monkey performing with an acrobat. This made perfect sense to the the bodies of the mother and the developing fetus are, after all, just two machines, so why shouldn't images in one machine be passed on to the other, and in this case, by the placenta? To be fair, the parties to the discussion did admit that it was impossible to give a detailed scientific account of the mechanism involved. Descartes natural philosophy left plenty of room for speculation that is not grounded in empirical evidence. But as the Cartesians realized, at least on this occasion, at some point speculation is just monkeying around with that. We're finally just about done with Descartes and his immediate influence, though of course his broader influence is something that will keep coming up in many episodes to come. I have to say that notwithstanding his spurious scientific theories, that influence was well deserved. Of course, my without any gaps approach means that I do try to champion the relevance of so called minor thinkers like the ones we've just been covering. From Codemois and La Forge, who have some claim to be the true inventors of occasionalism, to Raoult, who became the leading authority on Cartesian natural philosophy, to Steno, a pioneer in the use of anatomy as a critical science, and not least Poulain, who deployed Cartesian ideas in the cause of feminism. Yet even I have to admit that there was only one Descartes, and that if anyone deserves a reputation for being a major thinker, it's him. So I think you won't accuse me of indulging in monkey business if we devote one more episode to him and his legacy in the form of an interview on Cartesian medicine and science with Gideon Manning here on the history of philosophy without any gaps.