The Biology Book: From the Origin of Life to Epigenetics, 250 Milestones in the History of Biology (2015)

Mechanical Philosophy of Descartes

William Harvey (1578–1657), René Descartes (1596–1650)


Although René Descartes is best known for his philosophical writings and the development of mathematics, he also had a major impact on biological thinking. Called a pioneer of modern philosophy, he argued that the guarantors of truth are individuals and not the Church and was best known for “I think, therefore I am.” Following the family tradition, he was educated to become a lawyer (which he never practiced), but even as a young student, his true passion was mathematics. He conceived the Cartesian coordinate system, by which a point in space could be expressed as a set of numbers, and he developed analytical geometry, linking algebra and geometry, which served as the basis for the formulation of calculus by Isaac Newton and Gottfried Leibniz in the 1660s.

In 1628, William Harvey used mechanical analogies to describe the circulation of blood, and this is said to have inspired Descartes to formulate his mechanical philosophy. It was a mathematical and mechanistic approach that influenced Descartes’s perception of biology and that dominated much physiological research later during the nineteenth and twentieth centuries. In his 1637 Discourse on the Method, Descartes sought to explain everything in nature, with the exception of the human mind, in terms of principles of mechanics, mathematics, matter, and motion. The only realities were those that could be measured, such as size, shape, position, duration, and length; everything else, including the senses, was subjective and only existed outside the mind of the individual and had no physical reality. Just as the universe was a machine, so too was the organism’s body that contained the parts, arrangements, and movements needed to walk, eat, breath, and carry out all other functions.

Although Descartes recognized the distinction between animate and inanimate beings, he viewed animals to be no more than machines because, unlike humans, they lacked a soul that was responsible for intellect, volition, and conscious experiences; animals were incapable of using language, and they could not reason. He identified the pineal gland, located in the center of the brain, to be the “seat of the soul,” that acted through nerves to control the body.

SEE ALSO: Harvey’s De motu cordis (1628), Circadian Rhythms (1729), Hypothalamic-Pituitary Axis (1968).

With the exception of the human mind, Descartes sought to explain everything in nature in mechanical terms, including animals, which he compared to robots or complex machines.