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A-Z of Thought: Descartes
Kate Kirkpatrick
René Descartes (1596–1650) is the father of modern western philosophy. In fact, his ideas have been so influential that readers today often think them insignificant by virtue of their being so 'obvious'. Descartes was an archetypal polymath - in addition to being a rather good philosopher, he invented analytic geometry, which paved the way for calculus and made possible some of the greatest discoveries of physics.
What does this have to do with philosophy? The answer, for Descartes, is that maths offers us indubitable truth - the very thing philosophy should strive for. In the 17th century science was just beginning to come of age - when Descartes was a boy Galileo observed the moons of Jupiter - but this new science raised old questions about the reliability of the senses and the nature of reason: Can we trust what we see? What is the surest ground of knowledge?
These questions informed what philosophers call 'Descartes' sceptical project', which aimed to lay unshakeable foundations for human knowledge. He realized that he had occasionally been fooled by his senses - a stick looks bent when seen through water. Some people think they are kings, or that their heads are pumpkins made of glass. So he decided to be suspicious of all knowledge obtained by the senses, to disregard appearances in favour of something truer. His philosophy demands that we all establish for ourselves the truth of what we believe, and with certainty. This means pushing our doubts to the extreme - to absurdity, if necessary - in order to emerge on the other side with truth in our grasp.
In The Meditations, he puts this to the test, calling even maths into doubt. It is in this context that his most famous words, and his defeat of scepticism, are found: cogito ergo sum (I think, therefore I am). It is impossible that thoughts could be thought without a thinker - I cannot be deceived about the fact of my own existence. This thinking 'I' thus became the source of truth.
Descartes established the basic rules for philosophical investigation: the demand for certainty and immunity from doubt. This had implications not only for philosophy, but for the budding sciences and, of course, for religion. The unshakeable foundations were laid, and human knowledge came to rest on the certainty of the 'I' - the self became more authoritative than established teachings or the authority of others, including the Bible. This, too, was a revolutionary move in philosophy, though such subjectivity is now a firmly entrenched fixture of our culture.
Certainty is a worthy goal, and individuals should search for truth with fear and trembling. But there is more to it than we can find in ourselves.
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