All thought of something is at the same time self-consciousness [...] At the root of all our experiences and all our reflections, we find [...] a being which immediately recognises itself, [...] and which knows its own existence, not by observation and as a given fact, nor by inference from any idea of itself, but through direct contact with that existence. Self-consciousness is the very being of mind in action.

Phenomenology of Perception (ed. Psychology Press, 2002) - ISBN: 9780415278416