"Of all the immediate effects of pain and pleasure there is none more remarkable than the _will_; and though, properly speaking, it be not comprehended among the passions, yet as the full understanding of its nature and properties is necessary to the explanation of them, we shall here make it the subject of our inquiry. I desire it may be observed, that, by the _will_, I mean nothing but _the internal impression we feel, and are conscious of, when we knowingly give rise to any new motion of our body, or new perception of our mind_. This impression, like the preceding ones of pride and humility, love and hatred, 'tis impossible to define, and needless to describe any further."--(II. p. 150.) This description of volition may be criticised on various grounds. More especially does it seem defective in restricting the term "will" to that feeling which arises when we act, or appear to act, as causes: for one may will to strike, without striking; or to think of something which we have forgotten. Every volition is a complex idea composed of two elements: the one is the idea of an action; the other is a desire for the occurrence of that action. If I will to strike, I have an idea of a certain movement, and a desire that that movement should take place; if I will to think of any subject, or, in other words, to attend to that subject, I have an idea of the subject and a strong desire that it should remain present to my consciousness. And so far as I can discover, this combination of an idea of an object with an emotion, is everything that can be directly observed in an act of volition. So that Hume's definition may be amended thus: Volition is the impression which arises when the idea of a bodily or mental action is accompanied by the desire that the action should be accomplished. It differs from other desires simply in the fact, that we regard ourselves as possible causes of the action desired. Two questions arise, in connexion with the observation of the phenomenon of volition, as they arise out of the contemplation of all other natural phenomena. Firstly, has it a cause; and, if so, what is its cause? Secondly, is it followed by any effect, and if so, what effect does it produce? Hume points out, that the nature of the phenomena we consider can have nothing to do with the origin of the conception that they are connected by the relation of cause and effect. For that relation is nothing but an order of succession, which, so far as our experience goes, is invariable; and it is obvious that the nature of phenomena has nothing to do with their order. Whatever it is that leads us to seek for a cause for every event, in the case of the phenomena of the external world, compels us, with equal cogency, to seek it in that of the mind.