Cogito, ergo sum “I am thinking, therefore I exist” appears in the CSMK translation of Descartes's correspondence in French (“, ”) to colleagues at CSMK III 247. The earliest known translation as "I am thinking, therefore I am" is from 1872 by Charles Porterfield Krauth. As put compactly by Prof. Krauth (1872), "That cannot doubt which does not think, and that cannot think which does not exist. I doubt, I think, I exist." The phrase "cogito, ergo sum" is not used in Descartes's "Meditations on First Philosophy" but the term "the "cogito"" is used to refer to an argument from it. In the
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