. The phenomenology of certain mystical states is contrasted with the sense of “baseline” reality in an exploration of primary senses of reality. Nine theoretical and eight actual primary senses of reality are described. A neurophysiological model is presented to account for these states, and their possible adaptive significance is considered from an evolutionary perspective. Finally the state of absolute unitary being is contrasted with baseline reality, and their competing claims for primacy are evaluated in an epistemological context.