THE Unknown is universally apprehended in experience as tension-producing. This is understandable when one considers the child's earliest contacts with the world into which it is born. I shall not review the familiar psychological material except to bring it into focus with certain physiological observations. We know that the infant takes on new organic tasks from the moment of birth, e.g. the pulmonary circulation, breathing, temperature regulation, digestion and excretion. Though the mechanisms for performing these functions are present, the organism is 'physiologically awkward' and labile in its performance, so that the infant experiences extremes of fluctuation in its metabolic processes, and hunger levels which it has not heretofore known. Thus the smoothness of intra-uterine life cannot be reproduced even in the most favourable of situations, and the world is presented as an unknown (i.e. never-before-experienced) internal and external