Descartes insists, “[...] there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me [...]” (AT-VII, 25; CSM-II, 17). In what way can we draw evidence that our existence can be drawn from our being deceived? The interpretations that the earlier studies have shown is not a monolith. Then I will search for some inherent characteristics of deception, and analyse the construction of the reasoning, “if a deceiver deceives me, I exist.” To be concrete, I show: 1) that it is not “I exist” but “I think” that is concluded from the supposition “a deceiver deceives me/I am deceived by a deceiver”; 2) that the attributions of the self as a thinking thing, i.e. understanding, affirming, and denying (AT-VII, 28; CSM-II, 19), are discovered in the very supposition of a deceiver.