Which philosopher declared, "I think, therefore I am?"
And the answer: René Descartes.
Born in 1596, Descartes was a French philosopher, mathematician, and scientist, and considered one of the founders of modern philosophy. He thought that, if he doubted his own existence, then something must be doing the doubting. He concluded that the very fact that he doubted proved his existence.
Descartes was born into a modest rank of nobility that ultimately allowed him to move freely throughout social class and across space. He grew to be a pensive, withdrawn man, and after completing studies in France took to travel across Europe and the Netherlands, residing wherever he could find solitude. Throughout his teenage years and deep into adulthood, Descartes wrote prolifically. Personal pages, meditations, theories and theses (many of which have been lost to time) were all common creations of this young philosopher and mathematician. By the age of 25, Descartes had already devised a universal method of deductive reasoning.
Descartes' influence comes in many ways from his dependence on rational thought as a means of truth. As a rationalist, Descartes believed reason was the best guide for belief and action, and reason could be derived out of innate, human logic. This was largely disparate belief for other philosophers of Descartes' time. Most others (especially in France's then-homogenous religious state) relied upon God to find truth, often appealing their own logic to religious virtues. While Descartes was raised with religion, his philosophy of rational thought accepted God as omnipotent and argued that if he could picture Him as perfect, He was. The convergence of theology and rational thought is a primary reason that his meditations continue to be studied by philosophers and historians alike. By viewing the world's problems as the misuse of human thought in the existence of a perfect God, he surmised that such problems could be dissected and dealt with accordingly.
Descartes was monumentally influential to the world of modern philosophy and mathematics. Check out the video below to learn more about Descartes' life and teachings.