The problem of analysing and classifying the forces, faculties, or powers of the subsisting things and persons in the universe of our experience, belongs partly to Cosmology and partly to Psychology. In the latter it becomes mainly a problem of classifying our mental acts, functions, or processes—our states of consciousness. Apart from the question whether or not our mental faculties are really distinct from one another and from the human nature or substance itself of the individual, the problem of their proper classification is important from the point of view of method and of accurate psychological analysis. We have seen already ([69]) that the greatest scholastic philosophers are not unanimous in declaring the distinction to be real. But it is at least a virtual distinction; and even as such it gives rise to the problem of classification. It will be sufficient here to indicate the general principle on which the classification proceeds: Wherever the acts are adequately distinct they proceed from distinct powers; and the acts are adequately distinct when they have adequately distinct formal objects.[348] Potentiae specificantur per actus et objecta. The operation or act is the correlative of the power or faculty; and the formal object or term of the operation is the final cause of the latter, the end for which it is elicited. On this basis Aristotle and the scholastics distinguish two mental faculties of the higher or spiritual order, intellect and will; and in the lower or sense order of mental life they distinguish one appetitive faculty, sense appetite, and several cognitive sense faculties. These latter comprise the internal sense faculties, viz. the sensus communis or unifying and associating sense, the imagination, sense memory, and instinct; and the external sense faculties comprise sight, sound, taste, smell and touch.
81. Some Characteristics of Qualities.—(a) Qualities [pg 306] have contraries. Health and illness, virtue and vice, science and error, etc., are opposed as contraries. This, however, is not a property of qualities; it is not verified in powers, or in forms and figures; and it is verified in accidents which are not qualities, e.g. in actio and passio.
(b) Quality is the basis or “fundamentum” of all relations of similarity and dissimilarity. This attribute seems to be in the strict sense a property of all qualities. Substances are similar in so far as they have the same kind of qualities, dissimilar in so far as they have different kinds. Similarity of substances is the main index to identity of nature or kind; but it must not be confounded with the latter. The latter cannot always be inferred even from a high degree of similarity: some specifically distinct classes of things are very similar to one another. Nor, on the other hand, is full and complete similarity a necessary consequence of identity of nature: individuals of the same species are often very dissimilar, very unlike one another.
(c) Qualities admit of varying degrees of intensity. They can increase or diminish in the same substance, while numerically (and specifically) distinct substances can have the same kind of quality in different degrees. This is manifest in regard to “habits,” “passions” and “sensible qualities”. On the other hand, it is clearly not true of “form” or “figure”. Different individuals can have the same kind of “natural power” in different degrees. One man may be naturally of keener intellect and stronger will than another: the weak power was what Aristotle called ἀδυναμία (impotentia). But whether the natural powers of the same individual can themselves increase or decrease in strength or intensity—and not merely the habits that affect these powers—is not so clear. Operative powers are certainly perfected (or injured) by the acquisition of good (or bad) habits. In the view of those who deny a real distinction between natural operative power or faculty and substance, it is, of course, the substance itself that is so perfected (or injured).
This attribute, therefore, is not found in all qualities; but it is found in qualities alone, and not in any other category or mode of being.
How are we to conceive this variation in intensity, this growth or diminution of any quality, in a substance in which such change takes places? On this point philosophers are not agreed. By “degree of intensity”—“intensio vel remissio [pg 307] qualitatis”—we understand the degree (or change of degree) in which the same numerical quality affects the same part or the same power of its subject, thus rendering this part or power formally more or less “qualified” in some particular way. This is clearly something quite different from the extension of the same quality to different parts (or its withdrawal from different parts) of the same extended subject. In a corporeal, extended substance, there can accordingly be question of both kinds of change, intensive and extensive; while in a simple, spiritual substance there can obviously be question only of intensive change of qualities. And the fact of intensive change of qualities is an undeniable fact of experience. In what manner does it take place? Some authors conceive it as an addition or subtraction of grades or degrees of the same quality. Others, conceiving qualities as simple, indivisible entities or “forms,” and thence denying the possibility of distinct grades of any quality, conceive such change to take place by this simple entity affecting its subject more or less intimately, becoming more or less firmly rooted, as it were, in its subject.[349] And they explain this more or less perfect mode of inherence in a variety of ways, all of which are grounded on certain texts of St. Thomas:[350] the quality receives a new accidental mode whereby it “communicates itself to” the subject, and “informs” the latter, more or less perfectly; or, it is educed more or less fully from the potentiality of its subject, thus qualifying the latter in the degree in which it is educed from, and rooted in, the latter.
These explanations are instructive, as illustrating the view that the actual reality of the accidental mode of being consists in its affecting, determining, the subject in which it inheres. St. Thomas, professing that he can attach [pg 308] no intelligible meaning to addition or substraction of grades,[351] teaches that the habit of charity, for example, can be increased “secundum essentiam” by “inhering more perfectly,” “being more firmly rooted” in its subject; for, he says, since it is an accident, “ejus esse est inesse. Unde nihil est aliud ipsam secundum essentiam augeri, quam eam magis inesse subjecto, quod est magis eam radicari in subjecto. Augetur ergo essentialiter... ita quod magis ac magis in subjecto esse incipiat.”[352] And elsewhere he concludes with the words: “Ponere igitur quod aliqua qualitas non augeatur secundum essentiam, sed augeatur secundum radicationem in subjecto vel secundum intensionem actus, est ponere contradictoria esse simul”.[353]