Self-reflection focus on the beatific vision after death. The 13th century pope Innocent III wrote about the essential misery of earthly existence in his ""On the misery of the human condition"" – a view that was disputed by, for example, Giannozzo Manetti in his treatise ""On human dignity."" A famous quote of Shakespeare's Hamlet (II, ii, 115-117), expressing the contrast of human physical beauty, intellectual faculty, and ephemeral nature: René Descartes famously and succinctly proposed: "Cogito ergo sum" (French: ""Je pense donc je suis""; English: ""I think, therefore I am""). The Enlightenment was driven by a renewed conviction, that, 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