One somewhat speculative theme I’ve been developing here is the suggestion that our basic sentience or awareness has only a very loose unity, like that of a liquid. The idea is that sentience attaches primarily to our concrete thoughts, feelings, and perceptions, which can then flow together like droplets of water. Consciousness is not a matter of being a spectator of some internal theater. It attaches directly to the action of the play, so to speak. (See Ideas Are Not Inert; Imagination: Aristotle, Kant).
William James famously spoke of the “stream” of consciousness. I take this to be quite different from the unity of apperception that Kant talked about. The unity of a stream of consciousness is very loose and constantly changing, but that loose unity is a matter of fact. The unity of a unity of apperception on the other hand is quite strong, but it is a teleological tendency or a moral imperative, and not a matter of fact.
When we say “I”, that refers primarily to a unity of apperception — our constellation of commitments. This has much greater relative stability than our stream of consciousness. It is also what I think Aquinas was reaching for in claiming a strong moral unity of personal “intellect”. By contrast, one of the great modern errors is the equation “I am my consciousness”.