"The perception of what passes in a man's own mind.

I do not say there is no soul in man because he is not sensible of it in his sleep. But I do say he can not think at any time, waking or sleeping, without being sensible of it. Our being sensible of it is not necessary to anything but our thoughts, and to them it is and to them it always will be necessary.
John Locke (1632 - 1704)An Essay on Human Understanding (1688).

Locke clearly regarded consciousness as essential to thought as well as to personal identity. Locke's own definition of "consciousness" as "the perception of what passes in a man's own mind."Locke is one of the first to use the concept consciuosness in the psychological sense, although consciousness is closely intertwined with moral conscience that is, Latin conscientia For example, I may be held morally responsible only for the act of which I am conscious of having achieved; and my personal identity - my self - goes as far as my consciousness extends itself.

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