Cogito Ergo Sum

Even if you don’t know a thing about philosophy, you’ve probably heard the phrase “Cogito ergo sum” at least once in your life. This translates to “I am thinking, therefore I exist,” or “I think, therefore I am,” and it was an important thought in philosophical history. The thought was popularized by René Descartes in the 1600s after a long and frustrating thought experiment.

Descartes had been spending a long time searching for any idea at all that could be believed with undeniable certainty, but found that after rejecting all beliefs that could conceivably be doubted even in the slightest, he had absolutely nothing that he could call a certain truth. Think of it this way: an apple may look red to me, you, and everyone you ask, but Descartes would say that it is conceivably possible that the redness of the apple is just an artifact of the human eye or mind, and that the true color is impossible to be certain of. On an even deeper level, Descartes claimed that he couldn’t even be certain of the truthfulness of mathematical principles due to the fact that it is conceivably possible for them to all just be an elaborate trick being played on the people by some deity (or, today, we might say that it is conceivably possible that the physical and mathematical laws that govern our universe are actually programmed into our computer simulated reality by some higher life form).

At the end of it all, Descartes must have been frustrated. He had nothing he could hold as a baseline truth. But then a thought occurred to him: It was absolutely necessary that he, thinking of all of these things, existed. He found that this truth was so absolutely true that it could not be conceivably doubted, so he made it the fundamental principle of his philosophy. 

This idea is very interesting because it implies that you can only be sure of your own existence. If someone walks up to you and says, “Hey, I am thinking and therefore I exist,” you still cannot be certain that they are not a ghost, a computer simulation, a dream, hallucination, etc. You cannot even be certain that your own body actually exists. According to Descartes, the only thing one can be absolutely certain of is that his own mind exists. Everything else is completely uncertain.

Although this idea was made popular by Descartes, he did not invent it. There is evidence of “Cogito Ergo Sum” style thinking centuries before Descartes, but he was the first to state it in a philosophical context. His ideas are met with criticism, due to the fact that his attempt to achieve a logical approach to what can be known only raised more doubts than there ever were before. A lot of philosophers like Descartes’ initial idea, but do not like his solution to the problem of uncertainty, which relies on a belief in God being the omnipotent source of truth who would never deceive us. Many philosophers see this as a cop out, and as a result, the idea of skepticism is a philosophical hot topic to this day.