Desire is certainly a very extensive psychic _genus_ including many varieties which are noted by common introspection, and which are even denoted by special words. A wish is a momentary act of desire, longing is intense form; ambition and aspiration are desires for higher order of objects, as contrasted with desire for food or dress. The kinds as distinguished by object are numberless since any object may be desirable, and the realm of the desirable is coincident with the realm of the knowable. In the course of evolution we become aware of things and of states of consciousness, so that by feeling about them—having emotions—there may result the advantageous action with reference to them. This order, not consciously apprehended of course, is the natural order of psychic events, and one which, in tendency at least, always appears, even in latest evolutions. The desire to know what is the full experience value of things, curiosity, is an early acquirement, since complete cognition of object is obviously of the greatest advantage, especially to the weaker animals, as deer, who act wholly on the defensive. The very strong can afford to be largely indifferent to their environment. With reference to intensity, we can place forms from a positive to a negative pole. Thus with a famished man desire for food is first intense craving, becoming with continued eating moderate desire, then feeling of satisfaction, then of repletion, then negative, as aversion in passive form or satiety, then becoming active as disgust, and intense as loathing. Content, or desire satisfied, is not desire extinguished, rather it is an equilibrium wherein desire and its function are in continual equalizing action. When desire granted means all desire extinguished, with beings of any high tendency to activity _ennui_ is the result. Here, as Schopenhauer notes, wish for a wish develops. Even in complete pleasurable quiescence, there is desire for its continuance, which is only saying that there can be no complete quiescence short of coma, or else of a state where reality has never broken in, and experience is wholly unformed where the being cannot anticipate or note change. Pure and absolute content never occurs, and as a matter of fact never will, the point of transition in the desire gamut, in passing from positive to negative, being like a mathematical form, unreal and theoretical. When positive desire ends, negative desire springs up immediately, just as in the pleasure-pain gamut, where the indifference point of transition has no existence in reality.