Sandler postulates a safety principle in the ego which mediates between the development of the reality principle and the pleasure principle. All of the ego functions which subserve adaptation can be considered as being directed toward the mastery of excitation. The author makes a distinction between sensation and perception: the latter signifies an ego function whose chief purpose is to master incoming sensations by organizing sensory data, thus protecting the ego from trauma. Successful sensory integration is accompanied by anxiety reduction but it also contributes to a background feeling within the ego—a feeling of safety. This perception need not be tied to consciousness. The ego attempts to heighten the safety level, mainly through modification of the excitation which has passed the external protective barrier, and deliberate and purposive manipulation of the external world.