There are many important dimensions of epistemic evaluation, one of which is justification. We don’t just evaluate beliefs for truth, reliability, accuracy, and knowledge, but also for justification. However, in the epistemological literature, there is much disagreement about the nature of justification and how it should be understood. One of the controversies that has separated the contemporary epistemological discourse into two opposing camps has to do with the internalism-externalism distinction. Whereas internalists defend certain core assumptions about justification from the pre-Gettier tradition, externalists generally think that the traditional conception is untenable and should be replaced.

In this compilation thesis, I argue for, defend, and develop a particular brand of internalism, both in general and with respect to specific sources of justification. In papers 1 and 2, I defend a couple of well-known arguments for mentalism and accessibilism. Moreover, I also point out how prominent versions of these theses are vulnerable to serious problems (e.g., about over-intellectualization and vicious regresses). Part of my goal in the first couple of papers is to figure out what commitments the internalist should take on in order to avoid the externalist's objections, while at the same time receiving support from considerations that have motivated internalism in the past. In papers 3 and 4, I start from the assumption that mentalism is true and attempt to answer the following questions: 1) which non-factive mental states can play a justification-conferring role with respect to empirical belief? And 2) why does this set of states play the epistemic role it does? In response to question 1, I argue that all and only one's beliefs and perceptual experiences have justificatory relevance. In response to question 2, I argue that one's beliefs and perceptual experiences are one's strongly representational states, and that strongly representational states necessarily provide support to certain empirical propositions. Having done so, I then defend mentalism about scientific evidence from a couple of prominent objections in the recent literature. Lastly, in papers 5 and 6, I argue for a particular brand of internalism about testimonial and memorial justification and show how that position has a dialectical advantage over its main competitors.