regulate it, that it may render moderate and not excessive help, and at the seasonable time. For the emotional and unreasoning elements are subject to motions sometimes too quick and vehement, at other times too remiss and slow. And so everything we do may be a success from one point of view, but a failure from many points of view; as to hit the mark one thing only is requisite, but one may miss it in various ways, as one may shoot beyond or too short. This then is the function of practical reason following nature, to prevent our passions going either too far or too short. For where from weakness and want of strength, or from fear and hesitation, the impetus gives in and abandons what is good, there reason is by to stir it up and rekindle it; and where on the other hand it goes ahead too fast and in disorder, there it represses and checks its zeal. And thus setting bounds to the emotional motions, it engenders in the unreasoning part of the soul moral virtues, which are the mean between excess and deficiency. Not that we can say that all virtue exists in the mean, but knowledge and prudence being in no need of the unreasoning element, and being situated in the pure and unemotional part of the soul, is a complete perfection and power of reason, whereby we get the most divine and happy fruit of understanding. But that virtue which is necessary because of the body, and needs the help of the passions as an instrument towards the practical, not destroying or doing away with but ordering and regulating the unreasoning part of the soul, is perfection as regards its power and quality, but in quantity it is a mean correcting both excess and deficiency.
§ vi. But since the word mean has a variety of meanings—for there is one kind of mean compounded of two simple extremes, as grey is the mean between white and black; and there is another kind of mean, where that which contains and is contained is the mean between the containing and contained, as eight is the mean between twelve and four; and there is a third kind of mean which has part in neither extreme, as the indifferent is the mean between good and bad,—virtue cannot be a mean in any of these ways. For neither is it a mixture of vices, nor containing that which