Since the time of John Locke, many have thought that phenomena were collectively the passport to understanding the mind. Indeed, for many, phenomenal states constituted the mind. But we have seen (Parts One and Two) that phenomena, while indeed states of the mind, cannot bear the weight required for understanding those mental states that are most crucial to us as Lockean persons: our cognitive states – those states that make us thinking things. Phenomena may play an important role in perception (see chapter 4); but perception itself is a proposition-like state, the result not of passive processing, but of active and constructive processing. Even a state like pain, the most likely candidate for being a purely passive, phenomenal state, has been shown to involve proposition-like cognitive activity. And in Part Two, it has been argued that phenomenal consciousness, while indeed a type of consciousness, is only one type of consciousness – and the least important to our sense of ourselves as Lockean persons. As these first two parts were developed, it became more and more evident that another type of consciousness, apperceptive consciousness, is that state that is essential to our being Lockean persons. Part Three describes in more detail its importance.

And by doing so, Part Three mounts a defense of Cartesianism/Internalism – of Scientific Cartesianism – against twentieth-century anti-Internalist attacks on it. Considered thought about how we acquire concepts of the propositional attitudes (chapter 8) led to an Internalism about them, and an examination of the developmental data (chapter 9) led to a larger Internalist theory of concepts.