March 31, 1596 (a Sunday)

René Descartes

On this date, the French mathematician, anatomist, physiologist, and philosopher René Descartes was born in La Haye in the region of Touraine, France. He is often regarded as the first modern thinker to provide a philosophical framework for the natural sciences as these began to develop. In his Discourse on the Method of Rightly Conducting One’s Reason and Of Seeking Truth in the Sciences (1637) he attempts to arrive at a fundamental set of principles that one can know as true without any doubt.

Descartes is also known for the mind/body dualism he first articulated in his De homine (Treatise on Man), which he completed in Holland about 1633, on the eve of the condemnation of Galileo. When his friend and frequent correspondent, Marin Mersenne, wrote to him of Galileo’s fate at the hands of the Inquisition, Descartes became concerned for his own safety and refused to have De homine printed. Consequently, the first edition of this work was not published until 12 years after the author’s death.

Figure 1 from Descartes’ De homine (1664), depicting the human heart.

According to Descartes’ principle of dualism, the body works like a machine, has the material properties of extension and motion, and follows the laws of physics. The mind (or soul), on the other hand, is described as a nonmaterial thinking entity that lacks extension and motion, and does not follow the laws of physics. Descartes argued that only humans have minds, and that the mind interacts with the body at the pineal gland. [He chose the pineal gland because it appeared to him to be the only organ in the brain that was not bilaterally duplicated and because he believed, erroneously, that it was uniquely human.] In De homine, he wrote:

I suppose the body to be nothing but a statue or machine made of earth, which God forms with the explicit intention of making it as much as possible like us…

William Harvey’s recent discovery that the heart acts as a pump to circulate the blood had supplied additional arguments in favor of Descartes’ mechanical theory – in fact, Descartes probably did much to popularize the discovery. The Cartesian dualism set the agenda for philosophical discussion of the mind/body problem for many years after Descartes’ death.