Objection 1: It would seem that habits are not divided into good and bad. For good and bad are contraries. Now the same habit regards contraries, as was stated above (A, OBJ). Therefore habits are not divided into good and bad.
Objection 2: Further, good is convertible with being; so that, since it is common to all, it cannot be accounted a specific difference, as the Philosopher declares (Topic. iv). Again, evil, since it is a privation and a non-being, cannot differentiate any being. Therefore habits cannot be specifically divided into good and evil.
Objection 3: Further, there can be different evil habits about one same object; for instance, intemperance and insensibility about matters of concupiscence: and in like manner there can be several good habits; for instance, human virtue and heroic or godlike virtue, as the Philosopher clearly states (Ethic. vii, 1). Therefore, habits are not divided into good and bad.
On the contrary, A good habit is contrary to a bad habit, as virtue to vice. Now contraries are divided specifically into good and bad habits.
I answer that, As stated above (A), habits are specifically distinct not only in respect of their objects and active principles, but also in their relation to nature. Now, this happens in two ways. First, by reason of their suitableness or unsuitableness to nature. In this way a good habit is specifically distinct from a bad habit: since a good habit is one which disposes to an act suitable to the agent's nature, while an evil habit is one which disposes to an act unsuitable to nature. Thus, acts of virtue are suitable to human nature, since they are according to reason, whereas acts of vice are discordant from human nature, since they are against reason. Hence it is clear that habits are distinguished specifically by the difference of good and bad.
Secondly, habits are distinguished in relation to nature, from the fact that one habit disposes to an act that is suitable to a lower nature, while another habit disposes to an act befitting a higher nature. And thus human virtue, which disposes to an act befitting human nature, is distinct from godlike or heroic virtue, which disposes to an act befitting some higher nature.
Reply to Objection 1: The same habit may be about contraries in so far as contraries agree in one common aspect. Never, however, does it happen that contrary habits are in one species: since contrariety of habits follows contrariety of aspect. Accordingly habits are divided into good and bad, namely, inasmuch as one habit is good, and another bad; but not by reason of one habit being something good, and another about something bad.
Reply to Objection 2: It is not the good which is common to every being, that is a difference constituting the species of a habit; but some determinate good by reason of suitability to some determinate, viz. the human, nature. In like manner the evil that constitutes a difference of habits is not a pure privation, but something determinate repugnant to a determinate nature.
Reply to Objection 3: Several good habits about one same specific thing are distinct in reference to their suitability to various natures, as stated above. But several bad habits in respect of one action are distinct in reference to their diverse repugnance to that which is in keeping with nature: thus, various vices about one same matter are contrary to one virtue.