The French philosopher René Descartes (1596-1650) formulated the principle of certainty which he expressed in the proposition, "I think, therefore, I am." Discarding the old methods of explaining physical phenomena by means of final causes, he insisted that everything takes place mechanically and extended this principle to include physiological processes. He originated the science of analytical geometry and made important contributions to the theory of equations.

I Think ...

Frenchman Descartes, who was
Pondering life and the
Meaning of man,
Offered the following
Cogito, ergo sum
Thinking man's plan.

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