実践知と意志の弱さ : トマス・アクィナスの無抑制論

Abstract

The purpose of this paper is to examine Aquinas's theory about weakness of the will from two aspects. The first two chapters attempt to analyze how Aquinas interprets Aristotle's explanation of akrasiâ in the book 7 of Nicomachean Ethics. And then, in chapter 3 and 4, this theme is considered from a broader point of view. We should not overlook that Aquinas argues about moral weakness in the several, different contexts. This aspect, to the best of my knowledge, has never been examined properly so far. It is obvious that Thomistic description of an incontinent person is primarily based on Aristotle. The person in a state of incontinence has the right, universal principle, which is the major premise of his practical syllogism, but another type of knowledge, that is, the right, particular awareness (the minor premise) is absent or latent in this person. To put it another way, the incontinent does know generally what he should do, but he concentrates intently on that side of an object which provokes his desire, and cannot see the other side of it. As a result, his good moral principle has no power of producing a good action because the principle is not connected with the right judgment about the particular situation. The question now arises. Such a description doesn't seem to give a good account of our experience. It doesn't explain exactly and sufficiently a mental conflict or self-contradiction in a particular level, which is necessary for a comprehensive explanation of weakness of the will. In answer to this question, I propose the following discussion. In Aquinas's theory, there are two types of explanation of action. One is a practical syllogism model or a rule-case type. It consists of the major premise, the minor premise, and the conclusion. The other is an action theory model or an end-means type. This type has four phases or layers : intention, deliberation, decision, and execution. These two types of model are not unrelated and heterogeneous, but are complementary to each other, and therefore it is reasonable to attempt to unify both models. Based on this unified model, the lack of deliberation, decision, or execution can be regarded as the variations of weakness of the will. Finally, turning our eyes to the texts where Aquinas treats virtues and vices, we can see moral weakness in a new perspective. Aquinas lists the three functions of prudence : to deliberate, judge, and command. And he enumerates the vices or sins opposed to prudence in terms of these three functions, and labels them respectively precipitation, thoughtlessness, and inconstancy. It may safely assumed that these vices correspond to the variations of weakness mentioned above. In this way, we find the explanation of the phenomenon which can be called weakness of the will in the Aquinas's theory of virtue as well. Inconstancy means that a person has reached the good judgment and election or the right conclusion of the syllogism, but he doesn't step forward and perform his action. Although we can say that this is weakness of the will in the stricter sense, yet it is not incontinentia in Thomistic terminology. The range of incontinentia understood by Aquinas on the authority of Aristotle is narrower than that of what we call weakness of the will. It doesn't follow, however, that Aquinas fails to understand the nature of this phenomenon; he also thinks about moral weakness as a vice opposed to prudence, as already stated.