The Quality of Thought develops and defends the thesis that thinking is a kind of experience, characterized by a sui generis phenomenology, and draws out the implications of this thesis for dominant views in philosophy of mind, philosophy of language, and metaphysics. The view defended is radically internalist and intensionalist, and goes against received doctrines in philosophy of mind (externalism) and language (extensionalism). The book offers arguments for the thesis, refutations of classic externalism (Putnam and Burge), arguments that standard motivations for direct reference theories of names, indexicals, and demonstratives are not inevitable, and alternative accounts of their (and their conceptual equivalents') semantics. It also addresses outstanding challenges to the phenomenal intentionalist view of thought content, including the existence of unconscious thought, the elusiveness of conceptual phenomenology, the matching content problem, phenomenal compositionality, and the determination of conceptual reference.