James Mill in his ethical doctrine follows Bentham with little variation; but he shows very clearly what was the psychology which Bentham virtually assumed. I may pass very briefly over Mill's theory of conduct[556] in general. The 'phenomena of thought,' he says, may be divided into the 'intellectual' and the 'active' powers. Hitherto he has considered 'sensations' and 'ideas' merely as existing; he will now consider them as 'exciting to action.'[557] The phenomena consist in both cases of sensations and ideas, combined into 'clusters,' and formed into trains 'according to the sense laws.' We have now to consider the ideas as active, and 'to demonstrate the simple laws into which the phenomena of human life, so numerous and apparently so diversified, may all be easily resolved.' A desire is an 'idea' of a pleasant sensation; an 'aversion' an idea of painful sensation. The idea and the sensation are not two things, but two names for the same thing. Desire, again, has a 'tacit reference to future time' when applied to a given case. We associate these pains and pleasures with the causes; and in the important case our own actions are the causes. Thus the association produces the motive, and the readiness to obey the motive is, as Bentham says, the 'disposition.' Then, following Hartley, Mill explains the will. Bodily actions are muscular contractions, which are slowly co-ordinated by habit--association, of course, acting at every stage of the process. Now, it is a plain fact that muscular contractions follow 'ideas.' It is easy, then, to see how the 'idea of a pleasure should excite the idea of the action which is the cause of it; and how, when the idea exists, the action should follow.'[558] An 'end' is a pleasure desired, and gives the 'motive.' When we start from the motive and get the pleasure the same association is called 'will.' 'Free-will' is of course nonsense. We have a full account of the human mechanism, and can see that it is throughout worked by association, admitting the primary fact of experience that the idea causes the muscular contraction.