Abstract: The synchronic epistemic justification of a belief lies in it being a justified response to the believer's situation at the time, and this consists in its being based on adequate grounds. For a pure externalist, being based is being caused, grounds are a state that causes the belief, and (normally) the grounds are adequate, if the process by which they cause the belief is a token of a reliable type. Different externalist theories result from picking out different kinds of cause and selecting different types to which the token belief belongs. Theories become more and more internalist as the different elements of justification are understood in terms of factors to which the believer has introspective access—being ‘based’ as being ‘believed to be caused’, grounds as apparently basic beliefs, and their adequacy as their rendering the belief probable by a priori criteria.

Keywords: adequate grounds, Alston, basic belief, externalism, Goldman, internalism, justification, reliabilism, synchronic justification, Zagzebski,