Epistemology, the theory of knowledge, has traditionally competed for the primary role in philosophical inquiry. Sometimes epistemology has won, and sometimes metapysics, depending on the methodological and substantiative presuppositions of the philosopher.
The epistemologist asks what we know. Some philosophers have begun with an account of the nature of reality and then appended a theory of knowledge to account for how we know that reality. Plato, for example, reached the metaphysical conclusion that abstract entities, or forms, such as triangularity or justice, are real and all else is mere appearance. He also held that the, real is knowable, and he inquired into how we might know this reality. Aristotle, on the contrary, held that individual substances, such as individual statues or animals, are real, and inquired as to how we might have knowledge, especially general knowledge, concerning these substances.
It is hardly surprising that Plato and Aristotle produced vastly different theories of knowledge when they conceived of the objects of knowledge in such different ways. Their common approach, starting with metaphysics, we might refer to as metaphysical epistemology.
Other philosophers, most notably Ren Descartes, turned tables on the metaphysical approach by insisting that we must first decide what we can know about what is real and must remain ...