To the second one proceeds thus. It seems that habitude is not a determinate species of quality, because, as was said, habitude, insofar as it is quality, is called the disposition according to which the disposed is disposed well or badly. But this happens according to any quality, for both according to figure something can happen to be well or badly disposed, and similarly according to hot and cold, and according to all suchlike things. Therefore habitude is not a determinate species of quality.
Further, the Philosopher in the Categories says that heat and coldness are dispositions or habitudes, just like illness and health. But hot and cold are in the third species of quality. Thus habitudes or disposition are not distinguished from other species of quality.
Further, being able to be changed with difficulty [difficile mobile] is not a differentia pertaining to the genus of quality, but pertains more to change or undergoings [passionem]. But no genus is determined to a species through the differentia of another genus; rather, differentiae must come to a genus through itself, as the Philosopher says in Metaph. VII. Therefore, because habitude is said to be the quality of the difficult to be changed [difficile mobile], it seems that it is not a determinate species of quality.
But contrariwise is what the Philosopher says in the Categories, that one species of quality is habitude and disposition.
I respond that it must be said that the Philosopher in the Categories puts disposition and habitude among the four species of quality. Simplicius in his Commentary on the Categories assigns the differentiae of these species in this way, saying that some qualities are natural, which according to nature are within and always, but some are adventitious, which are effected from outside and can be lost. And those which are adventitious are habitudes and dispositions, differing according to being able to be lost with ease or with difficulty [facile et difficile amissibile]. But some of the natural qualities are according to that which something is potentially, and such are the second species of quality. Some, on the other hand, are according to what something is actually, and this either deeply or superficially. If deeply, such is the third species of quality; superficially, on the other hand, is the fourth species of quality, such as figure and the form that is the figure of what is animate. But this distinction of the species of quality seems inappropriate, for there are many figures and passible qualities that are not natural but adventitious, and many dispositions that are not adventitious but natural, such as health and beauty and suchlike. And, further, this is not appropriate to the order of the species, for always what is natural is prior.
And therefore in another way this distinction of habitude and disposition from other qualities must be taken. For quality properly involves mode of substance. Now mode is, as Augustine says, Super Gen. ad Litt., is what measure prefixes; wherefore it involves a certain determination according to some measure. And therefore just as that which according to material potential is determined according to substantial being is called substantial quality, so also that which according to subject's potential is determined according to accidental being is called accidental quality, which is also a certain differentia, as is clear from the Aristotle in Metaph. V. Now mode, or the determination of the subject according to accidental being, is able to be taken either in an order to the very nature of the subject or according to action and passion, which follow from the principles of nature, which are matter and form, or according to quantity. But if mode or determination of subject is taken according to quantity, such is the fourth species of quality. And because quantity, according to its notion, is without change and without the notion of good and bad, it therefore does not pertain to the fourth species of quality that something is done well or badly, passing swiftly or slowly. But the mode or determination of subject according to action and passion is found in the second and third species of quality. And therefore in both it is considered that something is done with ease or with difficulty, or that it is passing swiftly or enduring; but there is not considered something pertaining to the notion of good or bad, because change and undergoings do not have the notion of an end, but good and bad are said with respect to the end.
But the mode and determination of a subject in the order to the nature of a thing pertains to the first species of quality, which is habitude and disposition, as the Philosopher says in Phys. VII, saying of the habitudes of soul and body that they are a sort of disposition of the complete to the best; but I call the complete what is disposed according to nature. And because the same form and nature is end and cause for which something is done, as is said in Phys. II, in the first species good and bad are considered, and also what is able to be changed with easy or with difficulty [facile et difficile mobile], according as some nature is an end of generation and change. Wherefore in Metaph. V the Philosopher defines habitude as the disposition according to which something is disposed well or badly, and in Ethic. II he says that habitudes are that according to which we have ourselves well or badly toward passions; for when a mode is appropriate to the nature of a thing, then it has the the notion of good, and when it is not appropriate, then it has the notion of bad. And because nature is that which is first considered in a thing, habitude is put in the first species of quality.
To the first, therefore, it must be said that disposition involves a certain order, as was said; wherefore something is not said said to be disposed by quality, except in an order to something. And if well or badly is added, which pertains to the notion of a habitude, we must pay attention to the order to the nature which is the end. Thus according to figure, or according to hot and cold, someone is not said to be disposed well or badly, except according to an order to the nature of the thing, according to what is appropriate or inappropriate. Wherefore both figures themselves and passible qualities, according as they are considered appropriate or inappropriate to the nature of the thing, belong to habitudes or dispositions, for figure, insofar as it is appropriate to the nature of the thing, and color pertain to beauty, but hot and cold, according as they are appropriate to the nature of the thing, pertain to health. And in this way heat and coldness are put by the Philosopher in the first species of quality.
Wherefore the solution to the second is clear, although some solve it otherwise, as Simplicius says in the Commentary on the Categories.
To the third it must be said that this differentia, able to be changed with difficulty [difficile mobile], does not make habitude different from other species of quality, but from disposition. For disposition is taken in two ways: in one way, according as it is a genus for habitude, for in Metaph. V disposition is put into the definition of habitude; in another way, according as it is something divided from habitude. And the disposition that is properly said to be condivisible from habitude can be understood in two ways: in one way, as complete and incomplete in the same species, as it is called disposition, retaining the common name, when it is incompletely in something so as to be easily lost, but habitude when it is completely in something and is not easily lost. And thus disposition is habitude just like boy is man. In another way, they can be distinguished as different species subalternate to one genus, so that dispositions are said to be those qualities of the first species to which it is appropriate according to their notion to be easy to be lost, because they have transformable [transmutabile] causes, such as illness and health, but habitudes are said to be those qualities that according to their nature have what is not easy to transform, because they have unchangeable causes, like kinds of knowledge and virtues. And according to this, disposition is not habitude. And this seems to harmonize more with Aristotle's intention; wherefore, to prove this distinction, he draws upon [inducit] the common convention for speaking, according to which qualities that according to their notion are able to be changed with ease [facile mobiles] are, if by some accident are rendered able to be changed with difficulty [difficile moblies], are said to be habitudes, and conversely with qualities that by their notion able to changed with difficulty; for if someone has knowledge incompletely, so that he is easily able to lose it, he is said to be disposed to knowledge rather than to have knowledge. For which it is clear that the word 'habitude' involves a certain durability, but not the word 'disposition'. Nor does this stand in the way of 'being able to be changed with ease' or 'with difficulty' [facile et difficile mobile] being specific differentiae on the ground that these pertain to undergoing and change and not the genus of quality. For these differentiae, although they seem to have themselves accidentally toward quality, nonetheless designate the proper and per se differentiae of qualities, just as in the genus of substance accidental differentiae are often taken in place of substantial ones, inasmuch as essential principles are designated by them.
[Thomas Aquinas, ST 2-1.49.2. The Latin is here, the Dominican Fathers translation here.]
Aristotle divides the category of quality into four species:
(1) habitude and disposition
(2) natural capabilities and incapabilities
(3) passible qualities
(4) figure
His discussion strongly suggests that this is some immediate division of the category, but notoriously nobody knows quite what underlies the division. St. Thomas's (educated) guess is that the order is actually important, and this is a significant move, much more than it might seem. It's an important implication of this that there is a sense in which habitude and disposition is the kind of quality that has the strongest connection to what is natural to a thing. Virtue, knowledge, health, and beauty are all examples Aristotle uses of the first species of quality, and it's noteworthy that they can all be considered a sort of 'second nature' or a natural outgrowth of our original nature. It's also probably relevant, given the next two species (if, like Aquinas, we take the order to be significant), that habitude and disposition are easily the most active of the qualities; as we go down the list, it seems that we deal with things that depend more and more on the activity of something other than the quality, or for that matter the thing that has it, itself.
It's perhaps a little unexpected to find habitude regarded as more natural than natural capability, but by the latter Aristotle means the sense in which someone might be a 'natural wrestler' or naturally healthy, and it does seem that this is at least more attenuated than actual skill or actual health. Passible qualities are things like sweetness and color; by figure Aristotle seems originally to mean something like the quality of a quantity, e.g., a mathematical object being three-dimensional or circular or square-ish, or a number being cubic or prime. Most commentators have, I think, taken it a little more physically than that; perhaps 'jagged' or 'smooth' would be good examples in English.
