Apperception

Ap′per·cep′tion, n. [Pref. ad- + perception: cf. F. apperception.] (Metaph.) The mind's perception of itself as the subject or actor in its own states; perception that reflects upon itself; sometimes, intensified or energetic perception. Leibnitz. Reid.

This feeling has been called by philosophers the apperception or consciousness of our own existence. Sir W. Hamilton.