Cogito, ergo sum is "Since I doubt, I think; since I think, I exist"; with rearrangement and compaction, "I doubt, therefore I think, therefore I am", or in Latin, "dubito, ergo cogito, ergo sum". A further expansion, ("…—a thinking thing") extends the "cogito" with Descartes's statement in the subsequent Meditation, , or, in English, "I am a thinking (conscious) thing, that is, a being who doubts, affirms, denies, knows a few objects, and is ignorant of many …". This has been referred to as "the expanded "cogito"". Neither nor indicate whether the verb form corresponds to the English simple present or progressive aspect.
Cogito, ergo sum and that "I" know what "thinking" is. He suggested a more appropriate phrase would be "it thinks" wherein the "it" could be an impersonal subject as in the sentence "It is raining." The Danish philosopher Søren Kierkegaard calls the phrase a tautology in his "Concluding Unscientific Postscript". He argues that the "cogito" already presupposes the existence of "I", and therefore concluding with existence is logically trivial. Kierkegaard's argument can be made clearer if one extracts the premise "I think" into the premises "'x' thinks" and "I am that 'x'", where "x" is used as a placeholder in order to disambiguate