Rene Descartes' avowal, "I think therefore I am- elicits questions about the meaning of thought, the effect of existence and most fundamentally, in what sense he can be certain; what can Descartes leave un-doubted? The intricacy in determining the certainty of I think' and I exist' is that the two notions are interconnected. Therefore, differing analysis of what it is to think will have a profound impact on the question of whether Descartes can achieve certainty in knowledge of his own existence. Descartes' endeavor to attain certainty can be evaluated in relation to how well Descartes has overcome the universal doubt he has introduced in his first meditation. Now it is essential to consider the meaning of I', as it becomes very relevant and furthermore it is possible to argue that Descartes' use of I' reveals that his own explanation of what is certain is somewhat based on inherent beliefs. .
In many senses the statement I think' appears to be undoubted because "if anyone believes he is thinking or that he exists then necessarily he has a true belief."" Applying the Cartesian method, the assertion that I think' is exceptional since it is the only premise that has the property of having its truth confirmed by the act of doubting it. Descartes reveals that he has discovered a statement that is not trounced by the prospect of an evil demon situation' when he says "If I am in doubt, if I am entertaining the possibility that I might be deceived, then the very fact that I am around to entertain that doubt shows that I must exist-. Consequently, Descartes is presuming that his capability to entertain doubt, or think' is certain, which, based on the principle above, is not an irrational supposition. .
Prior to examining Descartes' assertion that he is thinking, the problem of what Descartes means by thinking should be answered. Provisional definitions of what it is to think can be separated into broad' and narrow' categories.