one's own existence.
There are only two mental operations by which true knowledge can be attained, says Descartes, and these are the methods of mathematics. Intuition is the understanding of self-evident principles. These are statements that are self-evident in that they prove themselves to reason, for to understand them is to know that they are absolutely true. They are propositions which no rational mind can doubt. The second method is deduction, by which Descartes means orderly, logical reasoning of inference from self-evident propositions. Descartes said that the chief secret of method was to arrange all the facts into a deductive, logical system. Descartes wishes to build a system of philosophy based on intuition and deduction, a system that will remain as permanent as and true as geometry. Descartes sets forth three requirement for the foundations of this philosophy:
1) Its certainty must be such that it is impossible to doubt, it is self-evident to reason, it is clear and distinct.
2) Its certainty must be ultimate and not depen
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