At the beginning of the second meditation, having reached what he considers to be the ultimate level of doubt — his argument from the existence of a deceiving god — Descartes examines his beliefs to see if any has survived the doubt. In his belief in his own existence he finds it is impossible to doubt that he exists. Even if there were a deceiving god (or an evil demon, the tool he uses to stop himself sliding back into ungrounded beliefs), his belief in his own existence would be secure, for how could he be deceived unless he existed in order to be deceived?