At the heart of Israel Rosenfield and Edward Ziff's inquiry is the nature of brain function. The sensory world is disordered and chaotic. There are no labels for tables, chairs, or airplanes, and indeed there are no colors, sounds, or smells, only photons, airwaves, odorant molecules, and so on, which are unlabeled and impossible to "know."

To make sense of this chaos, the brain must simplify the sensory inputs by creating, or inventing, the colors, sounds, smells, forms, and faces that are perceived in consciousness, which become a proxy for the chaotic world in which we live. The brain's ability to generalize and categorize these invented perceptions, and to relate them to one another, enables it to form memories, which are not fixed representations of things past, but a dynamic and malleable function of the brain that is relational.

When formation of these worlds breaks down, neurological differences arise. Although the mechanisms that transform sensory chaos into the simplified perceptions experienced in consciousness remain elusive, Rosenfield and Ziff relate what they have learned by means of imaging brain activity and by mapping the neural circuits that comprise memory traces. In addition, the authors offer perspectives for future studies of consciousness.