The terms ‘wish’ and ‘desire’ come to us from popular psychology, and cover a great variety of actual experience. If we are willing to speak somewhat arbitrarily, we may say that a =desire= appears when some particular tendency to action, which has present control of the nervous system, is thwarted by external circumstances, while the goal of action is still regarded as attainable; and that a =wish= appears when some tendency to action rises to momentary dominance, but is promptly met by inhibiting tendencies, while the goal of action is regarded as unattainable. This statement of the difference between desire and wish will not fit every case, for the reason that the terms are popular, and not technical, and that their meanings are not sharply distinguished either in ordinary speech or in psychology. The experiences themselves, if we seek to compare them with the experiences discussed in previous chapters, approach most nearly to _sense-feelings_. Desire is a straining-exciting, and wish a straining-subduing feeling; and both desire and wish may be either pleasurable or unpleasurable, according as the focal idea is the idea of result, of the goal of action, or the idea of its (present or permanent) inaccessibility. The existence of these ideas, however, and the play of associative tendencies which it implies, set desire and wish upon a higher plane of mental development than the sense-feelings; and the fact of direction, of the pressure of determining tendencies, marks another difference between the two kinds of experience. _This reference to sense-feeling reminds us of the doctrine, common to the associationist psychology and to modern popular psychology, that ‘pleasure and pain’ are the sole determinants of action._ Bain, for instance, tells us that “the proper stimulus of the will, namely some variety of pleasure or pain,” is always “needed to give the impetus”; “that primary constitution, under which our activity is put in motion by our feelings,” remains unchanged through the whole history of mind. Spencer, as we have seen (p. 86), regards it as a corollary to the general law of organic evolution that “pleasures and pains have necessarily been the incentives to, and deterrents from, actions which the conditions of existence demanded and negatived”; our actions are always ‘guided’ by pleasures and pains, immediate or remote. Leslie Stephen, who is in the main a disciple of Spencer, writes in his brilliant _Science of Ethics_: “pain and pleasure are the determining causes of action; it may even be said that they are the sole and the ultimate causes.” And, lastly,—though the list of quotations might be greatly extended,—Professor Sully asserts that “the prompting forces in our voluntary action are feelings.”