A primary and universal notion that cannot be strictly defined, although it can be described and illustrated. Its Greek equivalent, ποιότης, was coined by Plato (Theaet. 182A) and was used by Aristotle to designate one of the categories of being. It was translated by Cicero into Latin as qualitas. As used in logic, quality denotes a formal property of the copula whereby the proposition is affirmative or negative. As used by Aristotle and by scholastics in metaphysics, it designates one of the ten categories and means an accident (e.g., intelligent, white, robust) that makes an already essentially determined substance (e.g., man) to be of a certain kind. In modern philosophy, and generally in contemporary thought, quality refers to those characteristics of sensible reality whereby the senses are determined; for example, the color, sound, and shape of an object.
Aristotelian Division. According to Aristotle, the species of quality has the following four main divisions (Cat. 8b 25–11a 39). (1) Habits and dispositions. A habit is a firmly established condition of some nature. The man who, by repeated acts, becomes truly virtuous, acquires scientific knowledge, or develops an art conditions his nature in a certain way. Because this sort of quality is comparatively difficult to remove, it is known as habit. On the other hand, a condition of the subject that is easily changed, such as opinion, health, or disease, is called a disposition. (2) Power and incapacity. From the point of view of a nature's ability to operate, one can speak of the power or capacity to know, to will, and to resist pressure, as qualities of the being. In speaking of the powers of the soul, one frequently uses the term faculty (see faculties of the soul). When powers are weak, as resistance in soft things or nearsightedness in a man, they are called incapacities or impotencies. (3) Sensible qualities. These qualify the substance insofar as it is capable of affecting the senses, as colors, sounds, odors, hardness (see below).(4) Figure and shape. These are modifications of quantity and tell about the kind of line or figure, as curvedness, straightness, and triangularity.
Aristotle points out that while some qualities may have contraries (as justice and injustice) and some may admit of degrees (as white and whiter), these are the exception rather than the rule.
Primary and Secondary Qualities. This division of qualities has its roots in the works of Galileo galilei, R. descartes, and R. Boyle, and was fixed in modern terminology by John locke. The division corresponds almost exactly to the traditional distinction between common and proper sensibles. Common sensibles are the objects of more than one sense, as extension, shape, motion, and number. These are listed by Locke as primary qualities; but he added solidity to them. Proper sensibles are the objects of only one sense, as color and sound; and these in contemporary discourse are called secondary qualities.
The bases of differentiation for Locke and the scholastics, however, are quite different. Locke's viewpoint was the dependence of the secondary qualities on the primary, and his chief interest was in their gnoseological value. The scholastic interest was primarily psychological; its viewpoint was that of determining the formal object of each sense, or the relating of the proper sensible to the corresponding sense. Locke was influenced by current scientific theories, which stressed the mechanical explanations of the process of perception. For this point of view only the quantitative had mechanical importance. The qualitative as such was looked on as irrelevant, since it was thought to be merely the reaction of a sensitive organism to its environment.
Sensible Qualities. Sensible qualities are accidents that inhere in and determine corporeal substances and are perceived by the external senses; hence they are classified by their relation to the senses. Some qualities, being perceptible by one and only one sense, are referred to as the formal object of that sense: for sight, color; for hearing, sound; for taste, flavor; for smell, odor; for touch, tangibility (pressure and temperature). Other qualities are perceived by more than one sense; for example, extension can be sensed by sight, touch, and even taste. Qualities of this type include motion, rest, number, and shape. Since these are sensed by two or more senses (by means of the proper sensibles) they are called common sensibles. This classification into proper and common sensibles was traditional until the rise of modern philosophy.
Galileo and Descartes. While in some sense retaining this division, but not the terminology, Galileo and other philosophers and scientists after him claimed that the secondary qualities, being merely "apparent" qualities, should be reduced to and identified with their source in primary qualities. These were conceived to be the mathematical dimensions of matter in motion, which were themselves the truly real. When Descartes speaks of any reality he always means a substance (spirit as thought and body as extension) existing autonomously. Sensible qualities cannot be realities in any true sense, even as accidental determinations distinct from and inhering in the substance. For him this would mean that they were forms "joined to substance like little souls to their bodies" ("Letter to Mersenne," 1643, ed. Adam-Tannery 3:648). Although at times Descartes verbally refers to modalities or qualifications of substances, his interest is in substance as entire and present to his mind (Prin. Philos. 1.56; ed. Adam-Tannery 8:26).
Rationalism and Empiricism. Other rationalistic philosophers also enhance substance almost to the exclusion of qualities or accidents. B. spinoza could conceive only of attributes or modes of the one divine substance (Ethics 1. def. 4, 5) that do not determine but manifest and flow from the divine essence as corollaries follow a theorem. The monadology of G. W. leibniz presents a world made up of indivisible substances so closed off from all others that the classical meaning of accident loses all relevance. On the other hand, for the empiricists the notion of substance is an embarrassment. Locke sees it as a "something we know not what" to which qualities belong; G. berkeley denies material substance along with the extrasubjectivity of all qualities; and for D. hume, only ideas are perceived, and substance is suggested by the association of ideas.
Modern Scientists. When the empirical scientist discusses the objectivity and nature of qualities, he enters the domain of the philosopher, whose function it is to determine the categories of being. The scientist himself is interested in the quantitative and the measureable; even in his studies on colors and sounds, it is their quantitative aspects (such as wavelengths) that occupy him. This is as it should and must be. The difficulty arises when he begins to philosophize; when he does, he often follows Locke in the reduction of quality to quantity, in the at least implicit denial of the qualitative. But modern physicists who follow Locke "are deceived about the significance of their own discoveries. In describing perceptual experiences in terms of electrons and light-waves and so on they are explaining how it happens that we see things. They are not correcting our account of what it is we see"[M. Cranston, John Locke (New York 1957) 269].
Reality and Qualities. Since the time of Galileo and Descartes, most modern philosophers (and scientists generally) have conceded the objective existence of primary qualities. Locke very clearly taught that "ideas of primary qualities of bodies are resemblances of them, and their patterns do really exist in the bodies themselves" (Essay Concerning Human Understanding 2.8.15). Except for idealism and subjectivism, this position is generally maintained, although there are further differences in the explanation of how primary qualities are known.
Locke's Theory. Locke held that the mind has "no other immediate object but its own ideas" (ibid. 4.1.1.). So while quantity is truly a characteristic of reality, it is the idea of quantity that is known and that is asserted to correspond to reality. Scholastics disagree with this and hold that the real (not the idea of it) is the immediate object of both sensation and intellection.
On the question of the reality of secondary qualities there is even wider divergence. According to Locke, "the ideas produced in us by secondary qualities have no resemblance to them at all…. They are, in the bodies wedenominate from them, only a power to produce those sensations in us" (ibid. 2.8.15). For Locke, then, these qualities are neither the immediate object known, nor are they really objective. The reasons given by Locke for the subjectivity of secondary qualities, closely paralleling those of Descartes, revolve around such considerations as the way in which a jewel changes color in slightly different light conditions, or with the change of the observer's viewpoint; the fact that the same water can feel warm to one hand, cool to the other; that pounding an almond changes its color and taste; and so on.
Berkeley's View. Berkeley insisted that any argument against the objectivity of secondary qualities told even more strongly against the primary, and he concluded that all are equally subjective. The fact of the matter seems to be that if once it is conceded that ideas are the only immediate objects of the mind, one is in the strange position of never being able to know whether or not they do conform to anything "outside." In fact, in that case Berkeley might be right in looking on the outside as an unnecessary duplication, existing to no purpose. At least, if one is shut up in himself with only his ideas to contemplate, the opportunity will never be offered him to compare them with the "originals." He will then be in the position of sensing various "signals" and having no way to discriminate between them as purely subjective or truly objective.
Scholastic Teaching. Scholastics, while disputing among themselves about the nature of sensible qualities, do agree that: (1) they are not something merely subjective, but really exist in objects; (2) there is an accidental determination in the object, a dynamic extrasubjective quality, that is not equivalent to mere local motion (as Descartes held). With these points agreed, they dispute over whether sensible qualities exist formally in things, or merely fundamentally and causally.
"Perceptionists" (Aristotle, the early scholastics, T. pesch, C. Boyer, et al.) hold that such qualities exist formally in things. Some of their reasons are: that this is required for the objectivity of knowledge as a conformity to what is, that otherwise there is a danger of idealism, and that the scientific objections offered are not conclusive.
"Interpretationists" (J. balmes, D. mercier, M. de la taille, M. Maher, P. Siwek, et al.) hold for the immediate apprehension of real objective qualities by a virtual (not formal) assimilation, such as is had between a natural cause and its univocally determined effect. They claim that there is not merely a symbolic, but a true similitude. In this position they see no conflict with a realistic explanation of knowledge as truly objective, and they feel that scientific facts require it. A few of these facts will suffice here: (1) rotation of the Newtonian disk results in the seeing of white, whereas at rest the disk has the various spectral colors; (2) one and the same stimulus, e.g., electricity, causes different sensations in different organs; (3) sound varies with the distance, as experienced in the Doppler effect; this has also been verified of colors. On sound, even St. thomas aquinas says that "sound is only potentially in the sounding body" (In 2 anim. 16.441). A fuller discussion of the entire question and of other scientific facts is had in J. G. Moran's Psychologia 1:226 to 252.
Relation to Quantity. In scholastic philosophy both quality and quantity are said to be absolutely inherent accidents; that is, they are not relative to anything outside the substance they modify. Thus shape and color, considered in themselves, merely modify the substance and bespeak no relation to another being. Other accidents, such as action and passion, for example, are relative.
Moreover, quantity and quality are intimately related both metaphysically and noetically. Metaphysically, quantity is the ground for the sensible qualities. By this is meant that, while all accidents properly inhere in and are sustained in being by substance, yet no sensible quality exists except as extended; thus all qualities such as color, sound, and odor require a substance that is already quantified. In the order of knowledge it is in virtue of qualities that quantity is grasped. The eye, for example, is actuated by color, and it sees extension or shape by virtue of the color. With one's back to the ocean, one can not only hear the sound of the waves, but can perceive also their magnitude. So, while sensible qualities are the primary object of the senses, these also sense the species of quantity.
Intensification of Qualities. Because physical qualities are rooted in quantity, they are indirectly quantified through the quantity of the subject in which they exist. Apart from this, however, qualities can be quantified also by reason of their intensity, which is sometimes referred to as their quantity of perfection or of power. This quantification is essentially different from that of dimensive quantity and undergoes intensification and diminution in a special way.
Dimensive quantity is increased through simple addition (and diminished through subtraction) of homogeneous parts; thus the difference of two lengths is another length. This is true also of the quantity of a quality that is based upon the quantity of the subject in which the quality inheres; in this way, the quantity of heat is increased by the simple addition or juxtaposition of hot bodies. On the other hand, the intensity of qualities, not being additive or divisible with respect to homogeneous parts, is not increased or diminished in this way. Rather it is increased or decreased by the intensification or remission of the qualitative form, i.e., by a greater or less actualization of the quality in the subject in which it is found. This is how a body becomes hotter, with a greater intensity of heat than it had previously. Such intensification is not divisible in the same sense as extensive quantity. Thus the difference between two intensities is not an intensity of the same kind; for example, the difference in heat intensity between water at 100°C and water at 80°C is not the heat intensity found in water at 20°C. This difference between the dimensive and intensive quantities of qualities becomes of special significance when one attempts the measurement of qualities.
Measurement of Qualities. Since measurement has primarily to do with size, movements, weight, and the like, it is more proximately related to quantity than it is to quality. Yet the radication of quality in quantity provides one basis for speaking of the measurable aspects of quality. Another indirect way in which qualities can be measured, and particularly their intensification, is through the effect that they produce on another body, usually called an instrument. It is in this way that the physicist measures quantitative aspects of the intensities of heat, sound, color, and so forth. The psychologist similarly measures the effects of qualities on sense receptors in terms of their response to changes either in the environment or in the individual himself.
Modern psychophysics, prescinding from the philosophical aberrations of some of its exponents, is primarily interested in studying the correlations between the physical properties of stimuli and the psychological reactions of the organism to the various stimuli, in the hope of finding laws relating these measurements. Studies along these lines have more or less determined the threshold of sensation, or the minimum stimulus needed to activate a given sense, as well as the maximum stimulus that can be sensed. E. H. Weber and T. Fechner similarly studied the perception of increased stimulation. Weber felt that his experiments led to the "conclusion that the increase in stimulation resulting in a just noticeable increase in sensory experience must be a constant fraction of the original stimulus" [P. Siwek, Experimental Psychology (New York 1959) 104]. Fechner sought to express this in a mathematical equation, with questionable results.
Occult Qualities. The hidden forces, powers, or qualities discussed by late medieval and early Renaissance writers are generally known as occult qualities. The period in which these men lived was marked by a thirst for knowledge of nature, without the aid of present-day scientific methods and instruments. Thinkers such as J. L. Vives (1492–1540), deploring the dependence on Aristotle in the study of nature, advocated independent investigations and reflections on new observations. He urged the same empirical approach even in studying the soul. Another, Peter ramus (1515–72), also voiced discontent with previous methods of instruction, especially with Aristotelian logic, which he held responsible for the sad state of the universities. The spirit of the times was one of reflection and criticism, of revolt against authority and tradition in the name of reason and freedom, and interest gradually centered more and more on natural science.
Not content with the plodding means of observation and experiment and lacking refined instruments, many sought shortcuts. Some felt that there were latent powers or occult forces in nature that could be discovered and used in the service of man. The way to this was through magic, the use of secret arts, symbols, and mystic formulas; through astrology, the study of planetary influences on man and his world; and through alchemy, the magical transformation of metals. Agrippa von Nettesheim (1486?–1535) combined medicine with magic in the hope of learning about nature's occult qualities in herbs and minerals. Paracelsus (1493–1541) held that the physician must know not only medicine, but philosophy, astrology, and theology. He has to care for man, argued Paracelsus; and man belongs to this world through his physical body, to the sidereal world through his astral body, and to the spiritual world through his soul. So while he urged the correct use of available medicines to treat diseases, he sought to know the secret terrestrial and astral forces or occult qualities at work, and to control them by alchemy and magic. While this interest in the occult qualities of nature was extravagant and superstitious, it did foreshadow modern science in its attempt to control nature. As time went on alchemy evolved into chemistry; magic, into experiment; and astrology, into astronomy.
Qualifies and Modern Science. Because of the attitude modern scientists adopt toward sensible qualities, they generally tend to deny, or show little interest in, the qualitative as such. For example, the nonobjectivity of color, as distinct from measurable wavelengths, is almost axiomatic for scientists, and what can be said of color frequently applies to other qualities. Despite their rejection of sensible qualities, however, modern scientists are much concerned with nonsensible attributes of bodies, such as electricity, magnetism, gravity, and chemical affinity, which scholastic philosophers regard as pertaining to the qualitative order. Some of these were enumerated among the occult qualities by late medieval writers, because they cannot be directly perceived by any sense. Strictly speaking, however, they are not completely occult, because they are indirectly or reductively sensible from the effects they produce on instruments or experimental apparatus.
Granted that these are qualities, a considerable problem presents itself when one attempts to fit them into the Aristotelian category of quality. Most authors tend to locate them within the second species, as special types of active qualities. Thus gravity and impetus are regarded as active powers or potencies, because of their relation to mechanical motion. Electricity and magnetism, on the other hand, are frequently listed in the third species of quality because of their close relationship to light and color, particularly when these are regarded as forms of electromagnetic radiation.
Whether mass and energy should be regarded as qualitative attributes, in a scholastic sense, is a disputed question. Since these are primarily measurements and because mass is traditionally associated with "quantity of matter," there is some basis for including these under the category of quantity. Yet insofar as mass can also be regarded as a measure of gravitational or inertial tendency and since energy is commonly defined as an ability to do work, or to effect mechanical motion, there is also basis for enumerating these among the active qualities. The same appears to be true of other "force fields" studied in modern physics.
The difficulty in classifying these measurable attributes of bodies within traditional categories is explained by the distinctive procedures used in the physical sciences. Although the scientist investigates observable qualities of the material world, his description is usually in terms of working definitions that satisfy immediate needs. This usage, and the conceptual structures he evolves in its process, is pragmatically oriented and does not profess to offer a final explanation of the reality being described. In this way, standard scientific terminology admits of a multiplicity of philosophical interpretations when evaluated in terms of classificatory schemes that are like Aristotle's categories. The continued usage of qualitative attributes by the scientist, however, gives indication of his inability to work in quantitative terms alone and of his implicit admission that physical qualities are the means through which he comes to know the world of nature.
See Also: sensation; sense knowledge; knowledge; knowledge, theories of; epistemology.
Bibliography: l. m. rÉgis, Epistemology (New York 1959). f. c. copleston, History of Philosophy (Westminster, Md. 1946–); v.4, Descartes to Leibniz ; v.5, Hobbes to Hume. j. owens, An Elementary Christian Metaphysics (Milwaukee 1963). j. g. moran, Psychologia, 2 v. (Mexico City 1949). f. selvaggi, Cosmologia (Rome 1959). j. gredt, Elementa philosophiae Aristotelico-Thomisticae, 2 v. (11th ed. Freiburg 1956). r. j. blackwell, "The Methodological Function of the Categories in Aristotle," The New Scholasticism 31 (1957) 526–37. w. a. wallace, "The Measurement and Definition of Sensible Qualities," ibid. 39 (1965) 1–25. m. j. adler, ed., The Great Ideas: A Syntopicon of Great Books of the Western World, 2 v. (Chicago 1952) 2:513–26.
[r. f. o'neill]
qual·i·ty / ˈkwälətē/ • n. (pl. -ties) 1. the standard of something as measured against other things of a similar kind; the degree of excellence of something: an improvement in product quality | people today enjoy a better quality of life. ∎ general excellence of standard or level: a masterpiece for connoisseurs of quality | [as adj.] a wide choice of quality beers. ∎ archaic high social standing: commanding the admiration of people of quality. ∎ [treated as pl.] archaic people of high social standing: he's dazed at being called on to speak before quality. 2. a distinctive attribute or characteristic possessed by someone or something: he shows strong leadership qualities the plant's aphrodisiac qualities. ∎ Phonet. the distinguishing characteristic or characteristics of a speech sound. ∎ Mus. another term for timbre. ∎ dated Logic the property of a proposition of being affirmative or negative. ∎ Astrol. any of three properties (cardinal, fixed, or mutable), representing types of movement, that a zodiacal sign can possess. ORIGIN: Middle English (in the senses ‘character, disposition’ and ‘particular property or feature’): from Old French qualite, from Latin qualitas (translating Greek poiotēs), from qualis ‘of what kind, of such a kind.’