First and foremost a student of sleep physiology, Hobson recognized early that the hallucinatory experience we call dreaming itself involved conscious thought and declared that no theory of consciousness could be considered valid unless it encompassed the form and logic of dreams. An immense number of studies led to a simple and elegant conclusion that I will try to summarize very briefly. As we fall asleep, changes occur in three realms of brain function. Hobson describes these as 1) a decrease in the general level of activation throughout the brain, 2) a shift in the ability of the brain to take in information from outside the individual toward the ability to derive information from memory as an internal source, and 3) shifts in the modulation of neuronal firing resulting from alterations in the secretion of norepinephrine, serotonin, and acetylcholine. He has devised a marvelous cube to represent these three axes, and he uses it to show how waking consciousness, nondreaming sleep, and dream consciousness are related. Activation, modulation, and the ability to process sensory data are at their lowest in non-REM sleep and highest when we are awake; during the dreams associated with REM sleep all three modalities are at the midpoint of their scales and thus the center of his cube.