The purpose is a mental category. If we were restricted to the purely physiological standpoint of the earlier portion of our discussion in this book, we should have no real occasion to introduce the notion of purpose. It is true, of course, that there must be physiological counterparts, or parallels, of purposes which bear the same relation to behavior as do purposes in everyday thinking. Nevertheless, no useful result could be achieved by calling such physiological mechanisms purposes. But if we consider the psychological account of the typical emotional experience which we have given in the preceding chapter, we find that it has an aspect which corresponds closely with the ordinary idea of purpose. From the introspective standpoint, a purpose may be identified with what we have called "the image of the desideratum" in the emotional experience. It is a representation within consciousness, in imaginal form, of something which is desired. The "thing" which is thus desired is the satisfaction of the image, or its filling out by sensation so that it becomes a vivid and realistic perception. Thus, the man who is faced by the bear entertains the purpose of escape, as an image which faintly represents the terminal phase of the emotional experience--if the latter is to be successful.
It is evident that this definition of purpose rests upon a definition of desire. We have already suggested in the preceding chapter the meaning which we shall assign to the latter term. The course of a desire is characterized by an increase of affective intensity; whether this increase occurs in the region of positive or of negative values of this varible--consisting, of course, in the latter case, of a decrease of negative intensity. In other words, the course of a desiderative experience involves a positive value of da/dt (the rate of change of the affective intensity). However, it is probably necessary to go further than this and to say that the desiderative experience manifests the operation of a force which tends to produce such a change in the affectivity, even when the change in question is not actually realized. This means that the succession of images, acts of attention, etc., within the experience, are selected or rejected in accordance with their ability to minister to the affective increase in question. The embodiment of this force or tendency is to be looked for on the physiological side in the action of some retroflex mechanism. If the retroflex is of the negative kind, it will operate so as to inhibit all responses which do not succeed in removing it, and, consequently, will work toward the reduction of the unpleasantness of the corresponding experience. On the other hand, if the retroflex is of the positive variety, it will act in such a manner as to facilitate any form of response which continues its excitation, thus tending to maintain or to increase the positive affection in consciousness.
The desiderative or purposive consciousness may have many different forms and courses of change. The most primitive kind of desire presents no definite images of the "end." It constitutes the "blind purposeless striving," concerning which philosophers like Schopenhauer have waxed so eloquent; but it will recognize its "end" when it finds it. Such desire--prior to any experience which can establish associations informative as to the means by which the desire can be satisfied--will involve a process of volitional unrest; various kinaesthetic images will appear, be attended to, and be retained or rejected in accordance with affective consequences. All absolutely uneducated desires must be conceived as unpleasant. However, nearly all of the desires of human beings who have passed beyond the stage of early infancy are based upon previous, more or less accidental, affective experiences, or upon verbal information in association with such experiences.
Thus, positive desires are directed towards the acquisition of particular pleasant forms of experience which have occurred at least once before; whereas negative desires are directed towards the escape from unpleasant experiences, by means which have been demonstrated at an earlier time. A child will desire to avoid punishment, through some device which may have succeeded previously; or the child may desire candy because he has tasted it before and liked it. He may also desire particular playthings which he has never possessed, but has seen in the hands of other children, or has heard about as sources of amusement. In such cases, some initial perception arouses the desideratum --as in the case of the emotional experience--through an associative linkage. This association is based not merely upon the general principle of impression, but also upon that of retroflex selection, operative in the past.
The above account of desire is evidently hedonistic in character, since it portrays desire as an urge towards greater pleasantness. However, it is not necessary for us to imply, at least at the present stage in our argument, that there is any such thing as desire for pleasure, or relief from displeasure, in the abstract. Actual desires seem to relate to particular forms of pleasure or displeasure. Certain thinkers have claimed that desire or "interest" are independent of affective consequences and are directed solely towards concrete objects. The child desires candy, and not the pleasure which the confection will yield. We may agree, tentatively, with this proposition, although maintaining at the same time that the existence of such specific desires is dependent historically upon the affective aspects of similar prior experiences. The child would have no "interest" in the candy if it had not given him pleasure in the past. It is characteristic of the satisfaction of desires to yield pleasantness, or to involve a relief from unpleasantness.
This does not, however, preclude the possibility that desire may sometimes be generalized so that it applies explicitly to the affective aspects of all experience. A person with good powers of introspective observation, and a capacity for scientific thought, may be expected to notice that all specific desires are signalized by an affective trend in the direction of increased happiness. Using this observation as an experiential basis, such a mind might well begin to desire pleasure or release from relative displeasure regardless of content. But all such considerations fail to penetrate to the roots of the matter, since the thing which counts from the motivational standpoint is not the explicit content of the desiderative experience, but the laws which govern it. It is our thesis that these laws have a hedonistic form.
Now, purpose differs from primitive desire mainly by being more explicit and advanced. It is an educated form of desire; or desire is purposive insofar as it represents in advance the form of consciousness or experience which will bring satisfaction. Purposes may evidently vary in their persistence, complexity and the range of their applications. However, they are always characterized by some form of mental representation which is accompanied by a selective treatment of other mental representations, the latter appearing as a consequence of association with the purposive image and standing for possible means of its realization. Moreover, the trend of such purposive selection is away from the unpleasant and towards the pleasant. The satisfaction of a purpose is pleasant and its dissatisfaction is unpleasant. The pleasantness of satisfaction is to be attributed, not alone to retroflex processes, but to strong increases in conductance due to impressional principles. The purposive, or desideratum image, corresponds to a system of nervous connections which is prearranged and predisposed to rapid conductance increase. When the appropriate pattern of afferent excitations appears, it will particularly augment the conductances of such a predisposed neural arrangement.