Full Idea
We could think, feel, will and remember, and we could also 'act', and yet none of this would have to enter our consciousness. The whole of life would be possible without, as it were, seeing itself in a mirror.
Gist of Idea
All of our normal mental life could be conducted without consciousness
Source
Friedrich Nietzsche (The Gay (Joyful) Science [1882], §354)
Book Reference
Nietzsche,Friedrich: 'The Gay Science', ed/tr. Kaufmann,Walter [Vintage 1974], p.297
A Reaction
He credits Leibniz with this line of thought. Nowadays the unconscious aspects of thought are a commonplace, not just from Freud, but from neuroscience. We have no idea how conscious other animals are. Nietzsche attributes consciousness to communication.