The quote "I think, therefore I am" is Rene Descartes' famous cogito argument, and it is extremely important in epistemology. Using his own Method of Doubt, Descartes doubted everything that was provided by the fallible senses, as well as anything that could be part of a dream or an illusion created by an evil genius. This left him with one thing that he could be sure of— his existence. He reasoned that even if everything around him was an illusion, his mind must exist because otherwise he would never have been fooled. This quote is an extremely important argument in rationalism— as it is purely based on reason— and it is also relevant to solipsism. It illustrates Descartes' method of doubt, which is to doubt anything that comes from our senses or anything that could be an illusion.
