In recent years many influential philosophers have argued that philosophy is an a priori science, yet few epistemology textbooks discuss a priori knowledge at any length, focusing instead on empirical knowledge and justification. Although a priori knowledge has moved to centre stage, the literature remains either too technical or too out-of-date to make up a reasonable component of an undergraduate course.

Edwin Mares seeks to make the standard topics and current debates within a priori knowledge, including necessity and certainty, rationalism, empiricism and analyticity, Quine's attack on the a priori, Kantianism, Aristotelianism, mathematical knowledge, moral knowledge, logical knowledge, and philosophical knowledge, accessible to students.