The philosophy of quantum mechanics has often been conceived by physicists as a collection of dogmas concerning what can be measured, observed and known. To this branch of dialectics the present paper does not attempt to contribute, chiefly because it is written from the conviction that no part of science, nor any philosophy, can safely predict what may be feasible or knowable. Rather, this brief essay endeavors to expose the epistemology of quantum physics in a way which allows it to be recognized as an extension of the ordinary processes of cognition, as the continuation of a line which starts in sensory perception, leads straight through the methods of classical physics into quantum mechanics and shows no signs of terminating even there.