Finite verb to be omitted. For example, in the Latin sentence "cogito ergo sum" ("I think therefore I am") the finite verbs "cogito" and "sum" appear without an explicit subject – the subject is understood to be the first-person personal pronoun, and this information is marked by the way the verbs are inflected. In English, finite verbs lacking subjects are normal in imperative sentences: And also occur in some fragmentary utterances: The relatively poor system of inflectional morphology in English makes the central role that finite verbs play be often not so evident. In other languages, finite verbs are the locus of
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"