Chapter 51

Quality is that by which things are termed as being of such a sort. And again, quality is that from which those things which share it derive their names. Thus, from ‘prudence one who possesses prudence is said to be ‘prudent,’ and he who enjoys ‘warmth’ is said to be ‘warm.’

One should know that to tcoiov, or the being of such a sort, is more general than the quality. This is because the being of such a sort signifies both the quality and the thing which possesses it, that is, the quality, as ‘the warm,’ signifies that which has warmth. For, those who possess the quality are of such a sort, as, for example, those who have warmth are called ‘warm.’ And they who are warm are of such sort, but the warmth itself is a quality. Oftentimes, however, this quality is called of such a sort, and it is the same way with quantum and quantity.

Some of the qualities exist in animate and rational bodies, as various kinds of knowledge and virtues, sicknesses and health. And these are called habits and dispositions. Others exist in both animate and inanimate bodies, as heat and cold, form and shape, potency and impotency. Of these, some are potential and some actual. Now, if they are potential, they cause potency and impotency. If, on the other hand, they are actual, then either they will pervade the whole—as heat pervades the whole fire and as whiteness pervades all the milk and all the snow, and produce a passion and a passive quality —or they will be superficial and produce shape and form. There are, then, four kinds of quality: (1) habit and disposition, (2) potency and impotency, (3) affection and passive quality, and (4) shape and form.

Moreover, habit differs from disposition, because the habit does not change easily and is more permanent. Take prudence, for example, for one does not quickly change from prudence to imprudence. Similarly, knowledge may be a habit, too, for, when a person attains a thorough scientific understanding of something, this knowledge becomes firmly fixed in him and is hard to change. And the same is true of manliness, and discretion, and justice. Dispositions, however, are the easily moved and quickly changed, as, for instance, heat, cold, sickness, health, and the like. Thus, man is subject to these and he changes rapidly from hot to cold and from sick to healthy. These same, however—sickness, for example, health, and the like—will be habits if they are lasting and hard to change. Moreover, the term disposition is more general, because, since man is somehow ‘disposed" to them, they are both called ‘dispositions. On the contrary, that which is easily changed is called ‘disposition only.

A second kind of quality is that of potency and impotency. These are not in act, but they have a natural aptitude or power, or a natural inaptitude. Thus, we say that a boy is potentially musical because this boy, even though he does not actually possess the art of music, has an aptitude for its attainment. The brute beast, however, is unmusical, because it neither possesses the art of music nor is capable of attaining it. And that which is hard has the potentiality of not being speedily divided into parts.