The Importance of Dispositions
In the Summa Theologiae, Aquinas considers the question whether acquired dispositions are necessary for providing an analysis of human activity. Aquinas raises the question in the following way: ‘ Utrum sit necessarium esse habitum? In response to the claim that powers or capacities alone—what has been referred to above as Dispositions-1—are sufficient conditions for explaining human actions, Aquinas offered the following remarks, indicating that both dispositions as capacities and dispositions as acquired are necessary conditions for an analysis of human action.
Some capacities can be realized in more than one way. Thus if they are to be realized or actualized in one-way rather than another, it must be by something other than themselves. A capacity or power, however, which can be realized only in one way needs no acquired disposition to realize it. [. . .] For this reason, natural capacities or powers perform their activities without the assistance of acquired dispositions. This is so because they are intrinsically capable of actualization. (Summa Theologiae, I-II q. 49 a. 4 ad 3)
Where a capacity might be actualized in more than one way, as in the case of mastery of Riemannian geometry and of medieval French, an acquired disposition is necessary to provide a certain ease and facility in exercising the appropriate knowledge acts. Aquinas comments: ‘But if a form, like the soul, is such that it can act in more than one way, then it needs dispositions to bring it into the state appropriate to each action’ (Summa Theologiae, I-II q. 49 a. 4 ad 1).
Aquinas devotes an extended discussion to the need for acquired dispositions. He suggests that an intermediate state between a natural capacity—i.e. Disposition-1, and the actualization or realization of that capacity, which is Actuality-2—is necessary only if three conditions are met. In other words, the necessary conditions requiring the positing of acquired dispositions are the following:
First, the possessor of the state must be distinct from the realization of the capacity, and must stand to it in the relation of potentiality to actuality. There is no room for such a state or disposition, in a being whose nature is not made up of potentiality and actuality, and whose substance is identical with its action, and which has no goal but itself. This is obviously the case with God.
Secondly, it must be possible for the subject to actualize its potentialities in more than oneway, and with regard to more than one object. There is no room for states or dispositions in a being, which though unactualized in a certain respect, can be actualized only in one way. Such a subject already has by nature the appropriate relationship to the actuality in question. (Omitted here is a discussion of heavenly bodies.)
Thirdly, there must be more than one element whose presence is necessary if the subject is to actualize its potentiality in one of the several ways open to it. And it must be possible for these elements to be combined in different positions which will affect the subject favourably or unfavourably with regard to the form or operation in question. And so the simple qualities, which belong to each of the four elements in a manner determined by their nature, are not called ‘states’ or ‘dispositions’ but just ‘simple qualities’. The kind of things which we call ‘states’ or ‘dispositions’ are health, beauty, and other similar qualities which involve a particular proportion between elements which may be variously combined. This is why Aristotle [. . .] suggests that a disposition is a state and that a state is a relation between the parts of a complex, whether spatial, or potential, or specific.
Because, therefore, there are many beings whose natures and actions cannot be brought to completion without the presence of many elements that can be combined in various proportions, it follows that it is necessary that there should be such things as dispositions. (Summa Theologiae, I-II q. 49 a. 4; emphasis added)
