In philosophy
An 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 ' . In chapter XXVII "On Identity and Diversity" of Locke 's An Essay Concerning Human Understanding 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, as one of the oldest and most indispensable elements in the foundation of culture." John Locke does not use the terms self-awareness or self-consciousness though.
According to Locke, personal identity "depends on consciousness, not on substance" nor on the soul. We are the same person to the extent that we are conscious of our past and future thoughts and actions in the same way as we are conscious of our present thoughts and actions. If consciousness is this "thought" which doubles all thoughts, then personal identity is only founded on the repeated act of consciousness: "This may show us wherein personal identity consists: not in the identity of substance, but ... in the identity of consciousness." For example, one may claim to be a reincarnation of Plato, therefore having the same soul. However, one would be the same person as Plato only if one had the same consciousness of Plato 's thoughts and actions that he himself did. Therefore, self-identity is not based on the soul. One soul may have various personalities.
Self-identity is not founded either on the body or the substance, argues Locke, as the substance may change