Abstract
This thesis concerns the unity of consciousness - in particular the phenomenal unity of consciousness. The idea that consciousness is 'phenomenally unified' is the idea that if we attempt to characterise 'what it is like' for a subject just by listing all of the distinct experiences had by that subject at and over time, we will leave something out. We will leave out the unity of those experiences - the way in which those experiences feature together in consciousness. We can distinguish between the unity of consciousness at a time, and the unity of consciousness over time. I do not attempt to provide an account of the unity of consciousness at a time here - I focus instead upon the issue of unity over time. Some theorists - Dainton and Tye for instance - have claimed that it is possible to provide a single account of unity that solves both problems of unity in the same way. My contribution to the issue of unity at a time shall be to argue that such a single account is not possible, due to important differences in the phenomenological constraints that apply to the two problems. I proceed by providing an account of what exactly the constraints on an account of unity over time are, and argue that accounts that commit to the 'Principle of Simultaneous Awareness' cannot meet these constraints. I then provide a diagnosis of what may have been driving acceptance of such a principle in the first place - I argue that driving such acceptance is a faiiure to identify the metaphysical category of 'Occurrent State'. I propose that we can provide a successful and substantive account of diachronic unity only if we commit to thinking of a subject's phenomenal states as Occurrent States.