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Descartes

How Descartes Inspired Science

Kanan Purkayastha has both general and special theories about how the master rationalist inspired modern empirical science.

René Descartes (1596-1650) is one of the great thinkers in the history of humanity. Most of his work focused on philosophy, mathematics, and science, but he also dedicated many of his writings to physiology, and adopted a ‘mechanical’ vision of the world.

Descartes’ Discourse on Method (1637) is a good starting place for any discussion about how scientific thinking and methods developed. In this book, Descartes tells us how reason goes about its successful pursuit of truth in any area accessible to human mind. He states that “these long chains of reasoning, quite simple and easy, which geometers are accustomed to using to teach their most difficult demonstrations, had given me cause to imagine that everything which can be encompassed by man’s knowledge is linked in the same way” (p.41). From this, Descartes outlines the basic steps of his method. These can be summarised as:

(a) Do not accept anything just because it has been pre-established, if it is not evident to reason.

(b) Divide each problem into as many parts as necessary to make the reasoning simple and transparent;

(d) Take as many steps as needed, to verify that no logical step is omitted.

In his book Descartes and the Possibility of Science (1989), Peter Schouls suggests that “The Discourse… presents a functional definition of reason, where I use ‘reason’ in its broadest sense as the human ability to intuit, deduce and in the context of these processes to make proper use of imagination, sensation and memory” (p.1). In fact, Descartes proposed a method based on methodical doubt, analysis, synthesis and verification. These ideas contributed to what became the scientific method, and hence to the development of modern science. For instance, contemporary scientists use experimentation as a means to confirm or falsify whatever hypothesis is under consideration; and for Descartes, as Schouls observes, “experimentation… provides evidence for the correctness or incorrectness of a judgement made about a scientific statement or a body of such statements, namely, a judgement as to whether it is an account of the world in which we live” (p.88).

Werner Heisenberg, of Uncertainty Principle fame mentioned that Descartes’ most important ideas for the development of scientific thinking are contained in his Discours on Method. In his book Physics and Philosophy (1958), Heisenberg writes that Descartes “on the basis of doubt and logical reasoning tries to find a completely new and as he thinks solid ground for a philosophical system” (p.40). One of the beauties of science now is its encouragement to doubt everything – which is a contribution historically due to Descartes.

But now I’d like to briefly look at some of the ways in which Descartes has influenced or foreshadowed modern science more specifically.

Sensing The Environment

Descartes’ early model of nerve stimulation from his Treatise on Man (1632)

One of the deepest mysteries is the question of how we sense our environment. Descartes envisioned threads connecting different parts of the skin with the brain, and so imagined how heat against the skin sends mechanical signals to the brain, such that, for instance a foot touching an open flame would send a signal to the brain in the form of pain. He published this idea in his 1632 book L‘Homme, or Treatise on Man, where Descartes wrote, “if fire A is near foot B, the particles of this fire (which move very quickly, as you know) have force enough to displace the area of skin that they touch; and thus pulling the little thread C C, which you see to be attached there, they simultaneously open the entrance to the pore (or conduit) where this thread terminates (in the brain): just as, pulling on one end of a cord, one simultaneously rings a bell which hangs at the opposite end” (p.34-35, translated from the French by Thomas Steele Hall). As Hall mentions, “Descartes does not use the term ‘stimulus’ nor, in our sense, the term ‘response’. He usually employs the word ‘action’, to denote the elicitive events as well as the consequent events in the nerves.” This sort of language fits well with Descartes’ mechanical model of the world. But specifically, his nerve conduction model about how we sense our environment put us on the right path, and has inspired much Nobel Prize-winning research. Indeed, Joseph Erlanger and Herbert Gasser received the Nobel Prize in Physiology or Medicine in 1944 for their discovery of specialized sensory neurons that register changes in our environment. And in 2021, the Nobel Prize in Physiology or Medicine was awarded to David Julius and Ardem Patapoutian for their discoveries concerning nerve receptors for temperature and touch. Specifically, Julius and Patapoutian discovered how both temperature and mechanical touch stimuli are converted into electrical impulses in the nervous system. In their press release concerning this work, the Nobel committee cited how the work of René Descartes influenced these two Nobel Laureates.

The Anatomo-Clinical Method

The ‘anatomo-clinical method’ provides a systematic approach to the classification of neurological diseases based on inference from clinical signs, and especially from anatomical lesions (gaps or cuts) in the nervous system or the brain. The method was first developed by Jean-Martin Charcot, a clinical neurologist of the nineteenth century, who based his own research on it.

In fact, it is a two-part methodology. The first step of this method involves the careful documentation of clinical signs, such as abnormal behaviour or loss of specific aspects of perception or cognition – such as the ability to see in colour, or to recognise faces, etc etc. The second step involves an autopsy examination of the brain and spinal cord. Combining the clinical and anatomical data, Charcot was able to suggest concrete clinical–anatomical (specifically neurological) correlations. This method has helped us define the brain tracts and nuclei responsible for both normal and abnormal psychological signs, and was pivotal to a new classification of neurological diseases based on anatomy.

Now the anatomo-clinical method was strongly influenced by Cartesian thinking, and I want to use it as a prime example of how Descartes’ method works in a scientific setting. In the Discourse on Method, Descartes proposed reaching truth by not accepting any preconceptions that could not be demonstrated as true. Similarly, the anatomo-clinical method aims to reach a diagnosis without accepting conjectural elements that could not be scientifically demonstrated. In the Discourse, Descartes also proposed breaking each problem down into as many simple parts as necessary. Similarly, the anatomo-clinical method reaches its diagnosis by analysing the simplest symptoms and signs in each patient. Descartes proposed reconstructing the elements of an argument in an orderly way, from the simplest to the most complex. Similarly, in the anatomo-clinical method, the analysis is carried out gradually, starting from the simplest observable behaviours in order to investigate the complex structure of the nervous system. Indeed, I can see little difference between the Discourse’s approach to reaching the truth and the anatomo-clinical method for achieving disease diagnosis.

Several scientists received Nobel Prizes using the anatomo-clinical method. For example, in 1932 Sir Charles Sherrington was awarded the Nobel Prize jointly with Edgar Adrian for their discoveries on neuronal functions. This was to be the second Nobel Prize awarded in the field of the neurosciences, after the one shared in 1906 by the great Spanish anatomist Santiago Ramon y Cajal, the discoverer of the neuron, and the Italian Camillo Golgi, the inventor of the silver staining technique for looking at neurons under a microscope.

The Divisibility of Atoms

One of the most important properties of atoms in the atomist tradition is their indivisibility; indeed, a-tom is Greek for in-divisible. However, Descartes argued for the divisibility of atoms. This appeared in his Principles of Philosophy (published in 1644, later translated from the Latin by John Veitch), where Descartes wrote, “We likewise discover that there cannot exist any atoms or parts of matter that are of their own nature indivisible. For however small we suppose these parts to be, yet because they are necessarily extended, we are always able in thought to divide any one of them into two or more smaller parts and may accordingly admit their divisibility.” In his book Descartes’ Metaphysical Physics (1992), Daniel Garber suggests concerning this that “Descartes has no arguments intended directly to show that all bodies are naturally divisible. But he does think that in certain circumstances, at least, bodies are actually divided ad infinitum, or, as he might put it, ad indefinitum.” In other words, atoms may not be actually infinitely divided, but they can be divided indefinitely.

In fact, we now know that protons, electrons, and neutrons are subatomic particles that constitute atoms, and that some of these are made up of quarks (and so on, possibly). As a result, an atom can be divided. Ernest Rutherford discovered the proton, the first particle to be found in the nucleus of the atom. James Chadwick discovered the neutron, another particle in the nucleus. Murray Gell-Mann then proposed the existence of quarks, the particles that themselves make up protons and neutrons. They all earned Nobel Prizes in Physics. Perhaps to some extent their discoveries were inspired by the idea about the divisibility of atoms put forward by Descartes in 1644.

Motion

In the Principles of Philosophy, Descartes mentioned that “motion, in the ordinary sense of the term, is nothing more than the action by which a body passes from one place to another.” But in contrast to this simple definition, a fuller sense of motion defined by Descartes is as follows:

“In order to give it a determinate nature, that it is the transporting of one part of matter or of one body from the vicinity of those bodies that are in immediate contact with it, or which we regards as at rest, to the vicinity of other bodies.”
(Principles of Philosophy)

In defining ‘motion’ in this way, Descartes promoted the idea of space as understood through the change of ‘vicinity’ to other bodies. Of course, Albert Einstein developed the reigning theories of relativity, which also centrally relate motion to frames of reference, or as we might say, to the surrounding environment. And in 1975, the Nobel Prize in Physics was awarded to Professors Aage Bohr, Ben Mottelson, and James Rainwater, for their discovery of the connection between collective (whole body) motion and particle motion in atomic nuclei, and the development of the theory of the structure of the atomic nucleus based on this connection. But Descartes highlighted the importance of relative motion for physics centuries before all this.

Conclusions

In his book Dreams of a Final Theory (1992), the American physicist Steven Weinberg wrote, “the mechanical philosophy of Descartes had a powerful influence on Newton, not because it was right but because it provided an example of the sort of mechanical theory that could make sense out of nature” (p.134). Perhaps then we might even venture, no Descartes, no Newton?

Descartes himself thought that philosophy ought to provide the foundations of knowledge. This would require it to be prior to science. He wrote:

“Throughout my writings I have made it clear that my method imitates that of the architect. When an architect wants to build a house which is stable on ground where there is a sandy topsoil over underlying rock, or clay, or some other firm base, he begins by digging out a set of trenches from which he removes the sand, and anything resting on or mixed in with the sand, so that he can lay his foundations on firm soil. In the same way, I began by taking everything that was doubtful and throwing it out, like sand; and then, when I noticed that it is impossible to doubt that a doubting or thinking substance exists, I took this as the bedrock on which I could lay the foundations of my philosophy”
(Philosophical Writing of Descartes, ed. John Cottingham, p.366, 1984.)

If science needs foundations, then it is philosophy which provides them. René Descartes’ philosophy demonstrated this several centuries ago.

Kanan Purkayastha holds a PhD in Theoretical and Atmospheric Chemistry from the University of Bristol. He writes newspaper columns about science and philosophy. You can learn more about his work at kanan-purkayastha.org.uk.