Descartes: "I Think Therefore I Am" In following the rules, I will explain in detail what exactly is up for debate here, so this thread will not be locked. "I Think Therefore I Am", a common phrase (maybe the most common phrase), was written by Rene Descartes in the 1600's in his book Meditations II. In Meditations I, he "demolished" the certainty of anything existing. His reasoning was that there is no way to prove that his thoughts are deluded or being deceived, as humans have been wrong. Some of the examples he provided was you could not disprove that there is an evil supernatural being tricking the human mind or simple everyday optical illusions that trick the mind. The next day in Meditations II, he wrote that there is one thing that he could be completely certain of, that he existed. His logic was that doubts of certainty were because of deluded thoughts. If there are thoughts to delude, thoughts exist, and "I" (in this case, Descartes) is a thinking being that exists. Question: Does this common phrase which is often seen as self-evident provide solid proof to remove the doubt of "I" (in your case, yourself) existing. --- My personal opinion: Essentially descartes’ proof is: X is true. Y is true. Therefore, X is true. His argument is circular. "I think therefore I am" could also be "I am therefore I think". It’s the same thing as to say unicorns are pink, therefore unicorns surely exist. How could something be pink if it doesn’t exist. It’s tautological. It’s the equivalent of saying apples are red and they are delicious, therefore apples are surely red. You can replace the word think with ANYTHING. I eat therefore I exist. I dream therefore I exist. I walk therefore I exist. There’s no difference of what you say. Philosophy is a part of linguistics. We use words, as our only means, to try to prove our ideas to other people. There is so many limitations to language. We may exist, but we are unable to use words to prove it. Your thoughts?