The Philosophy of Descartes

Descartes' dualism of mind and body is a lasting legacy. Nowadays many people still believe the body is less well-known than the mind and that there is a mystery about how the mental and the physical can interact. His correspondence with Princess Elizabeth of Bohemia prompted him, late in life, to explore the union of mind and body in his last work, The Passions of the Soul. In retrospect, Descartes seems to have had two views of how mind and body might be related, one that the mind interacts with the body via a gland in the brain, the other that mind is spread all the way through body and intermingled with it. While neither view is satisfactory, it is still not clear nowadays how best to think about the relation of the mental to the physical. Copyright 2014 La Trobe University, all rights reserved. Please contact for permissions.

It might seem that Descartes' appeal to God in Meditation 4 as a guarantee that for the most part our memories can be trusted is not well-founded. By looking at the question of last-minute creation, a solution is proposed. Can we prove that we and our memories did not all come into existence just five minutes ago, or – as creationists have suggested – that the world and all its fossils did not just come into existence in 4004 BCE? Last-minute creation fantasies raise scenarios that are merely logically possible, but are not compatible with our best theories in geology, biology and other sciences. Descartes' appeal to God faces a different challenge, and objections to it are removed once the logic of his argument is made clear. Copyright 2014 La Trobe University, all rights reserved. Please contact for permissions.

By the end of the Meditation 2, Descartes is caught in a dilemma. On the one hand, everything can be doubted and so there is no prospect for secure and certain knowledge of the world. On the other hand, pure reasoning shows that he is undoubtedly a thinking thing, and this fact looks like a foundation from which other beliefs can be built. In order to proceed from the subjective certainty of the cogito, Descartes needs some basis on which to say that our memories (of previous investigations, deductions and insights) can generally be trusted. For this task, he introduces the idea of God, a being who has made the natural world and us, and has designed us so that we work well in the world. The lecture argues that nature, through evolution and natural selection, can substitute for God in scientific approach to solving Descartes' problem. Copyright 2014 La Trobe University, all rights reserved. Please contact for permissions.

One of Descartes' most striking arguments is the found in the treatment of a an example where he watches a piece of wax melt as he brings it close to a fire. By reflecting on how the same wax undergoes many changes, in colour, smell, shape, even from solid to liquid, Descartes concludes that it is through the mind, or intellect, not the senses, that we reach the most reliable knowledge of the world. Beliefs derived from the senses all involve inferences and the possibility of making mistakes in reasoning. By systematic use of reason, he hopes, we can start to build a scientific theory of the world that is reliable, and incidentally the search for some basic truth brings him back to the realization that mind is better known than, and separate from, body. Copyright 2014 La Trobe University, all rights reserved. Please contact for permissions.

The foundation of all science and other knowledge is found, according to Descartes, in the indubitable belief that I exist (the cogito claim). As soon as I have the thought, "I am thinking, so I exist", I realize this thought cannot be doubted: simply to have it, is to see that it is true. The problem is that in the first "Meditation", Descartes had introduced the possibility that even logic and mathematics is dubitable if we imagined our minds might be subject to manipulation by an evil demon or mad scientist. So why should the cogito be excepted? Has Descartes' commitment to hyperbolic doubt undermined his own project? Copyright 2014 La Trobe University, all rights reserved. Please contact for permissions.

An introduction to the life and work of Rene Descartes (1596 – 1650). In his collection of essays, called "Meditations", Descartes outlines a modern, rationalist philosophy, one that rejects the help of tradition and earlier theories in order to build a new system of knowledge and science based on only on certainty. Using only the power of reason, Descartes claims, it is possible to establish the sure foundation of all knowledge. Copyright 2014 La Trobe University, all rights reserved. Please contact for permissions.