People quite often speak of other individuals as deceiving themselves, and yet such an ordinary phrase has caused an immense concern in philosophic circles. In order to grasp why this is so we must realize fully exactly what the self-deceiver is doing – he is seemingly lying to himself. This, though, generates a paradox, for if a person is lying about something he necessarily must hold certain evidence which is not available to his victim. But how is such a thing possible within on human being? A person must somehow both know and not know the same thing simultaneously. This paper attempts to clarify the issues involved here – the paradox itself, the motive of self-deception, and the move into self-deception. In doing so we find that self-d...