In Explanatory Solutions to Skeptical Problems, Kevin McCain expands his previous work on the internalist dimension of the theory to cover external world skepticism. He also demonstrates how PE offers solutions to a host of other perennial skeptical problems including the problem of the criterion, the regress of justification, memory skepticism, and inductive skepticism. The promise that PE displays in responding to these problems makes it plain that it is a viable conception of epistemic justification worthy of careful consideration, and also that accepting internalism more generally doesn't leave one without reasonable responses to skeptical problems.