The famous philosopher, Rene Descartes, lived from 1596–1650. He was easily the most important philosopher of the seventeenth century and is one of the most significant philosophers in history. This “Father of Modern Philosophy” was a Catholic who spent most of his time in Protestant Holland. His most famous works were Discourse on Method, which was written in plain French, not academic Latin, and Meditations on First Philosophy.

Descartes believed he had a divine call for philosophical ideas. On a winter day in 1619, while serving in the Emperor’s army, he conceived the idea of reforming human learning. That night he had three dreams that he regarded as prophetic signs for his divine vocation.

Descartes was dissatisfied with all previous studies of philosophy. He was frustrated that there was not one point of philosophy that could not be disputed. As a professional mathematician, Descartes wanted to root philosophy in the same certainty that mathematics had. Thus, he wanted to establish a starting point for philosophy that was as certain as 2+2=4. For him, once this certain starting point could be established then a system of philosophy could be constructed from this foundation.

As Descartes began his pursuit for the starting point of philosophy, he decided that he needed to rid himself of anything that could be doubted. Thus, he started with “radical doubt.” For Descartes, even our five senses could not be trusted to give us a certain understanding of reality. In fact, Descartes said he even had to doubt that his own body existed. “What if I think I am sitting in a chair by this stove, but in reality I’m only dreaming?” he said. “Maybe there is an evil demon playing a trick on my senses,” said Descartes. “I may think I am sitting in this chair by a stove in a room, but the demon may be tricking me.”

Finally, after removing all things that he thought could be doubted, Descartes believed he had a breakthrough. He thought he found a starting point for philosophy—one thing that was beyond all dispute or doubt. What did he find?

Descartes asserted that the fact that he was thinking at all was proof that he existed. Even if he doubted his own existence, the very fact that he was involved with the activity of doubting must mean that he exists. Thus his famous declaration—Cogito ergo Sum, which means, “I think therefore I am.” From this alleged undisputable finding, Descartes believed he could build a system of philosophy.

Descartes’ theory had massive ramifications. Before Descartes, God and the Bible were often viewed as the starting points for understanding reality. Although a strong Christian man, Descartes did not start with God to understand reality. Instead, he started with himself. To be sure, Descartes believed God helped people understand things clearly, and he by no means meant to exclude God from philosophy, but he did not start with God to understand reality. Philosophers often say that Descartes shifted the focus in philosophy from God to the subject. Thus, the starting point for knowledge became the human thinker and human reasoning, not God.

This was a huge departure from how philosophy was done in the past. In his book, The Passion of the Western Mind, Richard Tarnas writes how significant Descartes’ approach was: “Infallibility, once ascribed only to Holy Scripture or the supreme pontiff, was now transferred to human reason itself. In effect, Descartes unintentionally began a theological Copernican revolution, for his mode of reasoning suggested that God’s existence was established by human reason and not vice versa.”

Descartes was talented in many areas. He was the founder of analytical geometry. He researched the nature of the eye and light. His view that there was a distinction between the mind and the body became known as “Cartesian Dualism,” a title named after him. Yet his most significant contribution was his attempt to establish a starting point for philosophy.

Descartes met an untimely death. Queen Christina of Sweden convinced Descartes to come to Sweden to be her personal tutor. A notoriously late riser, Descartes struggled with the 5 am philosophy lessons that Christina insisted upon. Descartes never adjusted and many feel that this schedule led to his death. He fell victim to the Swedish winter and died in 1650.