For motives to act, it is necessary not only that they should be present, but that they should be known; for, according to a very good expression of the schoolmen, which we referred to once before, _causa finalis movet non secundum suum esse reale; sed secundum esse cognitum_. For example, in order that the relation may appear that exists in a given man between egoism and sympathy, it is not sufficient that he should possess wealth and see others in want, but he must also know what he can do with his wealth, both for himself and for others: not only must the suffering of others be presented to him, but he must know both what suffering and also what pleasure is. Perhaps, on a first occasion, he did not know all this so well as on a second; and if, on a similar occasion, he acts differently, this arises simply from the fact that the circumstances were really different, as regards the part of them that depends on his knowing them, although they seem to be the same. As ignorance of actually existing circumstances robs them of their influence, so, on the other hand, entirely imaginary circumstances may act as if they were real, not only in the case of a particular deception, but also in general and continuously. For example, if a man is firmly persuaded that every good action will be repaid him a hundredfold in a future life, such a conviction affects him in precisely the same way as a good bill of exchange at a very long date, and he can give from mere egoism, as from another point of view he would take from egoism. He has not changed himself: _velle non discitur._ It is on account of this great influence of knowledge upon action, while the will remains unchangeable, that the character develops and its different features appear only little by little. Therefore it shows itself different at every period of life, and an impetuous, wild youth may be succeeded by a staid, sober, manly age. Especially what is bad in the character will always come out more strongly with time, yet sometimes it occurs that passions which a man gave way to in his youth are afterwards voluntarily restrained, simply because the motives opposed to them have only then come into knowledge. Hence, also, we are all innocent to begin with, and this merely means that neither we nor others know the evil of our own nature; it only appears with the motives, and only in time do the motives appear in knowledge. Finally we come to know ourselves as quite different from what _a priori_ we supposed ourselves to be, and then we are often terrified at ourselves.