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 itself is good and pleasant (...) and if one who sees is conscious that he sees, one who hears that he hears, one who walks that he walks and similarly for all the other human activities there is a faculty that is conscious of their exercise, so that whenever we perceive, we are conscious that we perceive, and whenever we think, we are conscious that we think, and to be conscious that we are perceiving or thinking is to be conscious that we exist... ("Nicomachean Ethics", 1170a25 ff.) Augustine of Hippo in "De Civitate Dei" writes "Si […] fallor, sum"