How We Know is intended as a summary (and a modest extension) of Objectivist epistemology. Binswanger's treatment of a wide range of epistemological issues is examined. Because his theory of propositions is inadequate and his philosophy of mind is an extreme form of dualism, Binswanger has added little to previous efforts by “official” Objectivists. As a work of epistemology in the broad sense, Binswanger's effort is fatally impaired. It is undone by his bifurcation between consciousness and the physics of the brain, which, if accepted, would largely deprive psychology and even computer science of their subject matter.