The stimuli for instincts are internal, such as the tissue deficit of hunger. These instinctual stimuli arise within the body and can best be described as needs. When a need such as hunger is aroused, it generates a state of physio- logical excitation in the body a physiological energy. This somatic energy, or need, is transformed in the mind into a wish. It is the wish-the mental representation of the body need--that is the instinct or driving force that motivates the person to behave so as to satisfy the body need, for example, the person may look for food. Thus the instinct is not the body state--the tissue deficit of hunger-but rather the transformation of that body need into a mental representation, a wish. We can see that, to Freud, the processes and functions of the mind-such as perception, thinking, remembering--depend upon activities of the body; indeed, they are manifestations of body processes. When the body is in a state of need, the person experiences a condition of tension or pressure. The aim of an instinct in every case is to satisfy the need and thereby reduce the state of tension. Thus, Freud's theory is essentially a homeostatic approach. We are motivated continually to restore and maintain the equilibrium of the body, to eliminate the tension and keep the body tension-free Freud believed that there is always a certain amount of instinctual tension