Thomas Aquinas

“ And thus a disposition becomes a habit, just as a boy becomes a man. Secondly, they may be distinguished as diverse species of the one subaltern genus: so that we call dispositions, those qualities of the first species, which by reason of their very nature are easily lost, because they have changeable causes; e.g. sickness and health: whereas we call habits those qualities which, by reason of their very nature, are not easily changed, in that they have unchangeable causes, e.g. sciences and virtues. And in this sense, disposition does not become habit. ”

“ But there are some habits, which even on the part of the subject in which they are, imply primarily and principally relation to an act. For, as we have said, habit primarily and of itself implies a relation to the thing's nature. ”

“ Further, habit implies relation to an act. But power implies sufficiently a principle of act: for even the natural powers, without any habits, are principles of acts. Therefore there was no necessity for habits.
Objection 3: Further, as power is related to good and evil, so also is habit: and as power does not always act, so neither does habit. Given, therefore, the powers, habits become superfluous. ”

“ 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. ”

“ After treating of human acts and passions, we now pass on to the consideration of the principles of human acts, and firstly of intrinsic principles, secondly of extrinsic principles. The intrinsic principle is power and habit ”

“ Wherefore the simple qualities of the elements which suit the natures of the elements in one single fixed way, are not called dispositions or habits, but "simple qualities": but we call dispositions or habits, such things as health, beauty, and so forth, which imply the adjustment of several things which may vary in their relative adjustability. ”

“ Consequently even shapes and passion-like qualities, in so far as they are considered to be suitable or unsuitable to the nature of a thing, belong to habits or dispositions: for shape and color, according to their suitability to the nature of thing, concern beauty; while heat and cold, according to their suitability to the nature of a thing, concern health. And in this way heat and cold are put, by the Philosopher, in the first species of quality. ”

“ The second condition is, that that which is in a state of potentiality in regard to something else, be capable of determination in several ways and to various things. Whence if something be in a state of potentiality in regard to something else, but in regard to that only, there we find no room for disposition and habit: for such a subject from its own nature has the due relation to such an act. ”

“ Therefore habit or disposition is not distinct from the other species of quality.
Objection 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. ”

“ It would seem that habits are not necessary. For by habits we are well or ill disposed in respect of something, as stated above. But a thing is well or ill disposed by its form: for in respect of its form a thing is good, even as it is a being. ”

“ And since the form itself and the nature of a thing is the end and the cause why a thing is made (Phys. ii, text. 25) , therefore in the first species we consider both evil and good, and also changeableness, whether easy or difficult; inasmuch as a certain nature is the end of generation and movement. ”

“ And therefore these constitute a special genus of things, which are comprised under the predicament of "habit": of which the Philosopher says (Metaph. v, text. 25) that "there is a habit between clothing and the man who is clothed." ”