SECOND ARTICLE [I-II, Q. 49, Art. 2]

Whether Habit Is a Distinct Species of Quality?

Objection 1:  It would seem that habit is not a distinct species of quality.  Because, as we have said (A. 1), habit, in so far as it is a quality, is “a disposition whereby that which is disposed is disposed well or ill.”  But this happens in regard to any quality:  for a thing happens to be well or ill disposed in regard also to shape, and in like manner, in regard to heat and cold, and in regard to all such things.  Therefore habit is not a distinct species of quality.

Obj. 2:  Further, the Philosopher says in the Book of the Predicaments (Categor. vi), that heat and cold are dispositions or habits, just as sickness and health.  Therefore habit or disposition is not distinct from the other species of quality.

Obj. 3:  Further, “difficult to change” is not a difference belonging to the predicament of quality, but rather to movement or passion.  Now, no genus should be contracted to a species by a difference of another genus; but “differences should be proper to a genus,” as the Philosopher says in Metaph. vii, text. 42.  Therefore, since habit is “a quality difficult to change,” it seems not to be a distinct species of quality.

On the contrary, The Philosopher says in the Book of the Predicaments (Categor. vi) that “one species of quality is habit and disposition.”

I answer that, The Philosopher in the Book of Predicaments (Categor. vi) reckons disposition and habit as the first species of quality.  Now Simplicius, in his Commentary on the Predicaments, explains the difference of these species as follows.  He says “that some qualities are natural, and are in their subject in virtue of its nature, and are always there:  but some are adventitious, being caused from without, and these can be lost.  Now the latter,” i.e. those which are adventitious, “are habits and dispositions, differing in the point of being easily or difficultly lost.  As to natural qualities, some regard a thing in the point of its being in a state of potentiality; and thus we have the second species of quality:  while others regard a thing which is in act; and this either deeply rooted therein or only on its surface.  If deeply rooted, we have the third species of quality:  if on the surface, we have the fourth species of quality, as shape, and form which is the shape of an animated being.”  But this distinction of the species of quality seems unsuitable.  For there are many shapes, and passion-like qualities, which are not natural but adventitious:  and there are also many dispositions which are not adventitious but natural, as health, beauty, and the like.  Moreover, it does not suit the order of the species, since that which is the more natural is always first.