Kant

The analytical unity of apperception is what I assert when I call a single representation mine, as if I were simply ascribing to it a property like that of being red; the synthetic unity of apperception is what I assert when I call all of my representations together mine, and what Kant is claiming is that the former depends on the latter – so to call a representation mine is not like calling one apple red at all, since that does not depend upon what I call any other apples.

This is obvious in the case of what Kant calls “empirical intuitions,” that is, immediate representations of particular objects involving sensation: when I have a sensory perception, or empirical intuition, of my copy of the Critique, it is because the particular object on my desk acts on me – by reflecting light waves that pass through the lenses of my glasses and eyes, and then stimulate my retinas, optic nerves, and so on – to put me into a certain mental state, namely, one in which it (at least) seems to me that there is a blue, rectangular object before me.

1 What can I know?
2 What should I do?
3 What may I hope?
4 What is the human being?
(Logic, 9:25)