a) Aristotle(992) distinguishes four different sets of qualities: (1) habit and disposition; (2) power and incapacity; (3) _passio_ (the power of causing sensations) and _patibilis qualitas_ (result of the modification of sense); (4) figure and circumscribing form (of extended bodies). As sanctifying grace manifestly cannot come under one of the three last-mentioned heads, it must be either a habit or a disposition. Habit denotes a permanent and comparatively stable quality, by which a substance, considered as to its nature or operation, is well or ill adapted to its natural end.(993) As a permanently inhering quality, sanctifying grace must be a habit. Hence its other name, “habitual grace.” The Scholastics draw a distinction between entitative and operative habits. An operative habit (_habitus operativus_) gives not only the power (_potentia_) to act, but also a certain facility, and may be either good, bad, or indifferent. An entitative habit (_habitus entitativus_) is an inherent quality by which a substance is rendered permanently good or bad, _e.g._ beauty, ugliness, health, disease. Philosophy knows only operative habits. But sanctifying grace affects the very substance of the soul. Hence the supplementary theological category of entitative habits. “Grace,” says St. Thomas, “belongs to the first species of quality, though it cannot properly be called a habit, because it is not immediately ordained to action, but to a kind of spiritual being, which it produces in the soul.”(994) There is another reason why grace cannot be called a habit in the philosophical sense of the term:—it supplies no acquired facility to act. This consideration led Suarez to abstain altogether from the use of the term “habit” in connection with grace,(995) and induced Cardinal Bellarmine to describe sanctifying grace as a _qualitas per modum habitus_,(996) by which phrase he wished to indicate that it imparts a supernatural perfection of being rather than a facility to act. To obviate these and similar subtleties the Council of Trent defined sanctifying grace simply as a permanent quality. Nevertheless scientific theology employs the term _habitus_ because it has no other philosophical category ready to hand. This defect in the Aristotelian system is somewhat surprising in view of the fact that besides the supernatural, there are distinctly natural qualities which “belong to the first species,” though they impart no facility to act but merely a disposition to certain modes of being, _e.g._ beauty, health, etc. There is also a positive reason which justifies the definition of sanctifying grace as a habit. It is that grace imparts to the soul, if not the facility, at least the power to perform supernaturally meritorious acts, so that it is really more than a _habitus entitativus_, namely, a _habitus_ (at least remotely) _operativus_.(997)