On the inductive search for definitions
But when it is asked what a thing is, for instance, what is the
human soul, what is charity or faith, it is a question of seeking for a real definition in accordance with laws laid down by Aristotle III in one of his works,(27) in which it is shown that the meaning of a
definition cannot be demonstrated, unless there are two definitions of the same thing, one of which, obtained by means of final or efficient causality, contains the reason for which of the other, namely, of the essential definition. Thus the circle and its circumference is defined as a figure, every point of which circumference is equally distant from the center, because it is formed by the revolution of a straight line around one of its extremities. But, with the exception of these cases, the definition cannot be demonstrated either a posteriori, as the existence of a cause can be demonstrated from its effects, or a priori, as a property is deduced from the essence; for the definition of a thing is the very means by which its properties are demonstrated, nor is there any process to infinity in this but if the real definition cannot be demonstrated, it is to be sought for by beginning with the nominal or conventional definition, which determines only what is the subject of discussion. The transition from the nominal to the real and essential definition is effected, as shown in the same work just quoted ,(28) by the gradual process of the division of the genera from the highest to the lowest, and by the inductive ascent to the specific difference from a comparison of similar and dissimilar things.(29) This method of finding definitions that truly expresses the reality and essence of things, is most admirably retained by St. Thomas.While several modern authors right at the beginning propose definitions that are some times very complex, as if they had received them by revelation, often not saying how they obtained them, St. Thomas at the beginning of each treatise inquires throughout several articles into the definition of the thing in question, for instance, the definition of charity, as being a friendship between God and man, and also a special and most sublime virtue. He also inquires into the definition of the four kinds of justice: equalizing, legal, distributive, and commutative, into the definition of prudence, and so on. In these articles there is no inquiry into the middle terrn of the demonstration, since the quest of the definition is not demonstration; but in this inductive inquiry the holy Doctor often adduces the most appropriate of observations, as Father Simon Deploige observed,(30) for instance, in the case of social matters. Thus the transition is made gradually from natural reason or common sense of mankind to philosophic reason.
This search for the definition is evidently of great importance, for all the demonstrations of the properties of anything have their foundation in its definition. In like manner, the direct division of any whole rests upon its definition; even universal principles are derived from rightly constituted and interconnected primary notions, and these principles, in the metaphysical order, are in every case true. Thus St. Thomas with profound penetration of thought decisively distinguishes between the antecedent and consequent wills from the very definition of the will, the object of which is good, this latter being formally not in the mind but in the things themselves. He says: "The will is directed to things as they are in themselves, and in themselves they exist under particular qualifications (here and now). Hence we will a thing simply, inasmuch as we will it when all particular circumstances are considered, and this is what is meant by willing consequently." (31) On the other hand, as stated in this same article, we will some good antecedently, as long as we will it when all particular circumstances are not considered, but according as it is absolutely good in itself; and this is to will it in a qualified manner and not simply. From these definitions thus established, St. Thomas deduces in the same article this most universal principle: "Thus it is clear that whatever God simply wills, takes place; although what He wills antecedently may not take place." But this double proposition virtually contains the whole teaching of St. Thomas about efficacious grace. If, indeed, the above-stated definitions of the consequent and antecedent wills have metaphysical validity, the same must be said of the principle that has its foundation in them. Then not even the least good act and most easy of performance right at the moment happens as dependent solely upon God's antecedent will, or without a decree of His consequent will, the causality of which is infallible, although it most admirably preserves intact human liberty, for, as just stated: "Whatever God simply wills, takes place; although what He wills antecedently may not take place." If any good act, even most easy to perform right at the moment, were to happen without such a decree of the consequent will, then the principle enunciated by St. Thomas would no longer he metaphysically true, and this would mean the complete ruination of his doctrine concerning God's foreknowledge and consequent will. If this principle were of no metaphysical validity, it would amount to nothing more than saying that salutary acts in the majority of cases do not take place unless they have been consequently willed by God, or, in other words, the universal Ordainer did not ordain all good things but only very many. This doctrine would be of no value either philosophically or theologically. But the principles that have been formulated in this order are not metaphysically and universally, or in every case, true unless they have their foundation in the due or correct definition of the subject. In this we clearly see the importance of searching for real definitions.
30. Cf. The Conflict between Ethics and Sociology (1938), pp.273 ff. In matters of faith the development of dogma consists in this transition, from a confused to a distinct notion, for instance, from the most confused notion of the human soul to this notion: that the human soul is by itself and essentially the form of the body. This proposition does not enunciate a property but the definition of the soul, which was known before in a confused manner. But if from the definition of man it is demonstrated that he is free, then this enunciates a property of his intellectual nature, and this is a new truth distinct from the definition of man. But often the search for the true definition entails more labor than the deduction of its properties from the same definition.
31. Summa theol., la, q. 19, a.6 ad lum.