Epistemology: philosophy of knowledge and cognition.
This is a central field of philosophy concerned with the nature, grounds and limits of knowledge: a generally unrecognized realm of value judgment and theory insofar as judgments rest on elective norms of “true” and “false” and “valid” and “invalid”.
Source: ‘What is Good? What is Bad? The Value of All Values across Time, Place and Theories’ by John McMurtry, Philosophy and World Problems, Volume I-III, UNESCO in partnership with Encyclopedia of Life Support Systems: Oxford, 2004-11.