Self-awareness early philosophical discussion of self-awareness is that of John Locke. Locke was apparently influenced by René Descartes' statement normally translated 'I think, therefore I am' ("Cogito ergo sum"). In chapter XXVII "On Identity and Diversity" of Locke's "An Essay Concerning Human Understanding" (1689) he conceptualized consciousness as the repeated self-identification of oneself through which moral responsibility could be attributed to the subject—and therefore punishment and guiltiness justified, as critics such as Nietzsche would point out, affirming "...the psychology of conscience is not 'the voice of God in man'; it is the instinct of cruelty ... expressed, for the first time,
Cogito, ergo sum ("If I am mistaken, I am") (book XI, 26), and also anticipates modern refutations of the concept. Furthermore, in the "Enchiridion" Augustine attempts to refute skepticism by stating, "[B]y not positively affirming that they are alive, the skeptics ward off the appearance of error in themselves, yet they do make errors simply by showing themselves alive; one cannot err who is not alive. That we live is therefore not only true, but it is altogether certain as well" (Chapter 7 section 20). In 1640 correspondence, Descartes thanked two colleagues for drawing his attention to Augustine and notes similarity and difference.