To what extent are meaning, on the one hand, and knowledge, on the other, determined by aspects of the 'outside world'? Internalism and Externalism in Semantics and Epistemology presents twelve specially written essays exploring these debates in metaphysics and epistemology and the connections between them. In so doing, it examines how issues connected with the nature of mind and language bear on issues about the nature of knowledge and justification (and vice versa). Topics discussed include the compatibility of semantic externalism and epistemic internalism, the variety of internalist and externalist positions (both semantic and epistemic), semantic externalism's implications for the epistemology of reasoning and reflection, and the possibility of arguments from the theory of mental content to the theory of epistemic justification (and vice versa).