Epistemology was the philosophical study of knowledge and of processes of knowledge acquisition.
In 2257, Spock endlessly quoted the First Doctrines of Logic, which stated in part, "Constructionism combines the epistemological thesis about what can be known with a meta philosophical view on the nature of philosophical questions." (DIS: "Light and Shadows")
In 2366, after the activation of Lal's heuristic associative pathways was successful, Data told her that she would begin processing information on epistemology, logic, metaphysics, and aesthetics. (TNG: "The Offspring")