I will investigate how well internalism holds as a thesis regarding theoretical or epistemic reasons (i.e. reasons for belief). If internalism seems true regarding epistemic reasons, then that would provide some evidence that internalism is also true regarding practical reasons, as there would be a unified relation that could explain reasons more generally across different normative domains. All else equal, a theory that can explain observations across a wide variety of general contexts in a non-ad-hoc fashion has more plausibility than a theory that must posit many different independent explanations to account for those same observations. On the other hand, if internalism seems false regarding epistemic reasons, then internalists will need to provide an explanation of why actions and beliefs are relevantly different enough to demand different fundamental conditions for their reasons. But it’s not clear to me how such an explanation can be given. After all, the concept of a reason is the same when discussing normative reasons for action and normative reasons for belief. Thus, we would expect the fundamental conditions that govern the presence of reasons to be the same as well. It seems to me then that the viability of internalism rests in part on the success of internalism as a theory regarding epistemic reasons. In what follows, I will argue that internalism is plausible regarding epistemic reasons.