77. Nature of the Accident Called Quality.—In the widest sense of the term, Quality is synonymous with logical attribute. In this sense whatever can be predicated of a subject, whatever logically determines a subject in any way for our thought is a quality or “attribute” of that subject. In a sense almost equally wide the term is used to designate any real determination, whether substantial or accidental, of a subject. In this sense the differential element, or differentia specifica, determines the generic element, or genus, of a substance: it tells us what kind or species the substance is: e.g. what kind of animal a man is, viz. rational; what kind of living thing an animal is, viz. sentient; what kind of body or corporeal thing a plant is, viz. living. And hence scholastics have said of the predicable “differentia specifica” that it is predicated adjectivally, or as a quality, to tell us in what the thing consists, or what is its nature: differentia specifica praedicatur in quale quid: it gives us the determining principle of the specific nature. Or, again, quality is used synonymously with any accidental determination of a substance. In this sense magnitude, location, action, etc., though they determine a subject in different accidental ways, nevertheless are all indiscriminately said to “qualify” it in the sense of determining it somehow or other, and are therefore called “qualities” in the wide sense of “accidents”. Hence, again, the scholastics have said that inasmuch as all accidents determine or qualify their subjects, they are predicated of these qualitatively, and may be called in a wide sense “qualifications” or “qualities”: omnia genera accidentium qualificant substantiam et praedicantur in quale.
It is in this wide sense that we use the term when we say that the (specific) nature (or “kind”) of a thing is revealed by its “qualities”; for the nature of a thing is revealed by all its accidents. And when we infer the nature of a thing from its activities, in accordance with the maxim Qualis est operatio talis est natura, we must take the term “operatio” or “activity” to include the operation of the thing on our cognitive faculties, the states of cognitive consciousness thus aroused in us, and all the other accidents thus revealed to us in the thing by its “knowledge-eliciting” action on our minds.
But the term Quality has been traditionally restricted, after Aristotle, to designate properly one particular category of accidents distinct from the others and from substance.
A definition proper of any genus supremum is of course out of the question. But it is not easy to give even a description which will convey an accurate notion of the special category of Quality, and mark it off from the other accident-categories. If we say with Aristotle that quality is “that whereby we are enabled to describe what sort (ποιόν, quale) anything is”[323]—e.g. that it is white by whiteness, strong by strength, etc.—we are only illustrating the abstract by the concrete. But even this serves the purpose of helping us to realize what quality in general means. For we are more familiar with the concrete than with the abstract: and we can see a broad distinction between the question: “What sort is that thing? Qualis est ista res?” (Quality), and the question: “How large is that thing? Quanta est ista res?” (Quantity), or “Where is that thing?” (Place), or “What is it doing? What is happening to it?” (Actio et Passio), or “What does it resemble?” (Relation), etc. This will help us to realize that there are accidental modes of being which affect substances in a different way from all the extrinsic denominations of the latter ([60]), and also in a different way from Quantity, Relation, and Causality; and these modes of being, whereby the substance is of such a sort, or in such a condition, we call qualities. And if we inquire what special kind of determination of the substance is common to qualities, and marks these off from the other accidents, we shall find it to consist in this, that quality is an accidental mode of being which so affects the substance that it disposes the latter well or ill in regard to the perfections natural to this particular kind of substance: it alters the latter accidentally by increasing or diminishing its natural perfection. We have seen that no created substance has all the perfection natural to its kind, tota simul or ab initio ([46]); that it fulfils its rôle in existence by development, by tending towards its full or final perfection. The accidental realities which supervene on its essence, and thus alter its perfection within the limits of its kind or species, are what we call qualities. They diversify the substance accidentally in its perfection, in its concrete mode of existing and behaving: by their appearance and disappearance they do not change the essential perfection of the substance ([46]), they do not effect a substantial change; but they change its intermediate, [pg 288] accidental perfection; and this qualitative change is technically known and described as alteration[324] ([11]).
Hence we find Quality described by St. Thomas as the sort of accident which modifies or disposes the substance in itself: “accidens modificativum sen dispositivum substantiaein seipsa,” and by Albertus Magnus somewhat more explicitly as “the sort of accident which completes and perfects substance in its existence and activity: accidens complens ac perficiens substantiam tarn in existendo quam in operando”.[325] This notion will be conveyed with sufficient clearness if we describe Quality as that absolute accident which determines a substance after the manner of an accidental “differentia,” affecting the essential perfection of the substance in regard to its existence or to its activity.
Hence (1) the Pure Actuality of the Infinitely Perfect Being cannot admit qualities, inasmuch as quality implies only a relative and limited perfection; (2) the qualities of a corporeal substance are grounded in the formative principle which gives that substance its specific nature and is the principle of its tendency and development towards its final perfection, whereas its quantity is grounded in its determinable or material principle; (3) the essential differentiating principles of substances—being known to us not intuitively, but only abstractively and discursively, i.e. by inference from the behaviour of these substances, from the effects of their activities—are often designated not by what constitutes them intrinsically, but by the accidental perfections or qualities which are our only key to a knowledge of them. For instance, we differentiate the nature of man from that of the brute beast by describing the former as rational: a term which really designates not the essence or nature itself, but one of its fundamental qualities, viz. the faculty of reason.
78. Immediate Sub-Classes of Quality as Genus Supremum.—On account of the enormous variety of qualities which characterize the data of our experience, the problem of classifying qualities is not a simple one. Its details belong to the special [pg 289] sciences and to the other departments of philosophy. Here we must confine ourselves to an attempt at indicating the immediate sub-classes of the genus supremum. And in this context it will not be out of place to call attention to a remarkable, and in our view quite erroneous, trend of modern thought. It accompanied the advent of what is known as atomism or the mechanical conception of the universe, a conception much in vogue about half a century ago, but against which there are already abundant evidences of a strong reaction. We refer to the inclination of scientists and philosophers to eliminate Quality altogether as an ultimately distinct category of human experience, by reducing all qualities to quantity, local relations, and mechanical or spatial motions of matter (cf. [11]). In this theory all the sensible qualities of the material universe would be really and objectively nothing more than locations and motions of the ultimate constituents of perceptible matter. All the chemical, physical and mechanical energies or forces of external nature would be purely quantitative dispositions or configurations of matter in motion: realities that could be exhaustively known by mathematical analysis and measurement. And when it was found that qualitative concepts stubbornly resisted all attempts at elimination, or reduction to quantitative concepts, even in the investigation of the material universe or external nature, scientists and philosophers of external nature thought to get rid of them by locating them exclusively in the human mind, and thus pushing them over on psychologists and philosophers of the mind for further and final exorcism. For a time extreme materialists, less wise than daring, endeavoured to reduce even mind and all its conscious states and processes to a mere subjective aspect of what, looked at objectively, would be merely matter in motion.[326] It can be shown in Cosmology, Psychology, and Epistemology that all such attempts to analyse qualities into something other than qualities, are utterly unsatisfactory and unsuccessful. And we may see even from an [pg 290] enumeration of some of the main classes of qualities that such attempts were foredoomed to failure.
Scholastic Philosophy has generally adopted Aristotle's division of qualities into four great groups:[327] (1) ἕξις ἢ διάθεσις, habitus vel dispositio; (2) δύναμις φυσικὴ ἢ ἀδυναμία, potentia naturalis vel impotentia; (3) ποιότητες παθητικαί καὶ πάθη, potentiae passivae et passiones; (4) μορφὴ ἢ σχῆμα, forma vel figura. St. Thomas offers the following ground for this classification. Since quality, he says,[328] is an accidental determination of the substance itself, i.e. of the perfection of its concrete existence and activity, and since we may distinguish four aspects of the substance: its nature itself as perfectible; its intrinsic principles of acting and receiving action, principles springing from the formative, specific constituent of its nature; its receptivity of change effected by such action, a receptivity grounded in the determinable or material principle of its nature; and finally its quantity, if it be a corporeal substance,—we can likewise distinguish between (1) acquired habits or dispositions, such as health, knowledge, virtue, vice, etc., which immediately determine the perfection of the substance, disposing it well or ill in relation to its last end; (2) intrinsic natural forces, faculties, powers of action, aptitudes, capacities, such as intellect, will, imagination, instinct, organic vital forces, physical, chemical, mechanical energies; (3) states resulting in a corporeal being from the action of its milieu upon it: the passions and emotions of sentient living things, such as sensations of pleasure, pain, anger, etc.; the sensible qualities of matter, such as colour, taste, smell, temperature, feel or texture, etc.; and, finally (4) the quality of form or shape which is a mere determination of the quantity of a corporeal substance.
This classification is not indeed perfect, for the same individual quality can be placed in different classes when looked at from different standpoints: heat, for instance, may be regarded as a natural operative power of a substance in a state of combustion, or as a sensible quality produced in that substance by the operation of other agencies. But it has the merit of being an exhaustive classification; and philosophers have not succeeded in improving on it.
Qualities of the third and fourth class do not call for special [pg 291] treatment. In the third class, Aristotle's distinction between ποιότητες παθητικαί (qualitates passibiles) and πάθη (passiones) is based upon the relatively permanent or transient character of the quality in question. The transient quality, such as the blush produced by shame or the pallor produced by fear, would be a passio;[329] whereas the more permanent quality, such as the natural colour of the countenance, would be a passibilis qualitas. The “passions” or sensible changes which result from certain conscious states, and affect the organism of the sentient living being, are included in this class as passiones; while the visible manifestations of more permanent mental derangement or insanity would be included in it as passibiles qualitates. We may, perhaps, get a fairly clear and comprehensive notion of all that is contained in this class as “sensible qualities” by realizing that these embrace whatever is the immediate cause or the immediate result of the sense modification involved in any act or process of sense consciousness. Such “sensible qualities,” therefore, belong in part to the objects which provoke sense perception, and in part to the sentient subject which elicits the conscious act. One of the most important problems in the Theory of Knowledge, and one which ramifies into Cosmology and Psychology, is that of determining the precise significance of these “sensible qualities,”—and especially in determining whether they are qualities of an extramental reality, or merely states of the individual mind or consciousness itself.