custom or practice which gives rise to the virtues? would be this, The practice which produces virtues is "the avoidance of excess and defect." Medio tutissimus ibis. And thus the answer to our sixth question, which, I think, is closely and logically affiliated to the questions which have gone before it, brings us to the celebrated Aristotelic position, that virtue is a mean or middle between two extremes, which in themselves are vices. We shall consider this position for a few minutes.
47. We are now able to define virtue, which we could not do until this sixth question was answered. Previous to that question we had declared that virtue was a habit. But there are other habits besides the virtuous. Vice may be called a habit. Habit, therefore, is only the genus under which virtue falls. We want its differentia. Do we obtain this when we say that virtue is a habit produced by practice? We certainly do not, for all habits are produced by practice. But we do obtain this differentia when we look to the answer to the sixth question, and when we say, Virtue is a habit which aims at the mean. Every habit which steers clear of excess on the one hand, and of defect on the other hand, partakes of the quality of virtue. And accordingly, Aristotle's definition of virtue is, that it is a disposition or state or habit (genus) of aiming at the mean between two opposite vices (difference).
