Quality

To ask what quality a thing has is to ask what sort of thing it is, and not how much of it there is, where it stands, or how it is related to something else. The idea of quality therefore covers a wide field. It includes the old logical category, set beside quantity and relation. It includes the properties and attributes by which one body is told from another. It includes the sensible qualities, the colours, sounds, tastes, heats and hardnesses through which the world is first known. In the modern period it also includes the disputed distinction between primary and secondary qualities.

Quality is a great idea for these books because it lies where logic, physics, the theory of knowledge and the theory of taste meet. A single question passes through all of them: do the qualities we perceive belong to things, or only to us? The Harvard Classics follow that question from Plato’s snow to Berkeley’s cherry, and beyond it into economics, aesthetics and the Bhagavad-Gita’s quite different doctrine of the qualities of nature.

The oldest treatment is logical. In the Phaedo, Plato separates heat and cold from fire and snow, which possess them¹. A quality, on this view, is something a thing has rather than what the thing is. Augustine recalls the scheme of categories that sorts what may be said of a man by his quality, his quantity, his relations, his place and his time². By Milton’s day this scheme was part of school learning: in one of his college exercises Quantity and Quality come forward as the next of the Predicaments³. Hobbes keeps the logical framework but gives it a nominalist turn. Abstract names such as life, motion and heat, he holds, mark the accidents and properties by which one body is distinguished from another⁴.

Voltaire shows how much rode on the word “quality” in the new physics. He defends Newtonian attraction as a quality inherent in matter, and he is careful to set it apart from the occult qualities of the ancients⁵. The scholastic habit of explaining effects by hidden qualities had become a reproach. A modern quality had to be one that experiment could exhibit and measure.

Before turning to that natural science, it is worth noting a branch of the idea in which quality means excellence. Here it stands against quantity and against price rather than beside them. Adam Smith separates the utility of an object from its purchasing power, treating them as distinct properties⁶. He also refuses to let the two be confused causally. The inferior quality of Scottish dairy produce, he argues, is the effect of its low price rather than its cause⁷. Smith admits frankly that quality is a very disputable matter, which makes comparisons of the price of cloth across ages uncertain⁸. What resists measurement troubles the political economist.

Carlyle reverses the emphasis. He holds that whoever fixes the quality of a work may fix its quantity, so that easy satisfaction with oneself yields rapid output⁹. Speed of production, he insists, is beside the point; the only question is how well the work is done¹⁰. In Smith quality complicates exchange value. In Carlyle quality is the measure of worth and quantity the distraction.

In the natural sciences, qualities become the observable marks by which substances are identified and their nature inferred. Faraday’s lectures make this a matter of demonstration. Different particles differ in bulk and weight, and hydrogen is shown to be extremely light by soap bubbles and by comparison with air, water and platinum¹¹. Vapours, he observes, are always transparent, though they may be coloured, sometimes by mixing gases that are themselves colourless¹². Carbonic acid is characterized entirely by its qualities: it will not burn, dissolves slightly in water, turns lime-water white, and is heavier than air¹³. For Faraday, to know a substance is to know its properties as they show themselves under test.

Colour receives the most searching scientific treatment. Voltaire reports the Newtonian teaching that the colours of bodies arise from their disposition to reflect certain rays and absorb others¹⁴. He also traces colour to the differing refrangibility of the rays themselves¹⁵. Kelvin, writing much later from the standpoint of the wave theory, likewise explains the colour of a body by which parts of the spectrum it transmits¹⁶. On this account colour is a real disposition of bodies toward light. That leaves open whether the red we see is in the body, in the light, or in the eye. The physicists describe the disposition. The philosophers ask about the seat of the quality.

That question is the centre of the modern controversy. Hobbes states the radical answer early and without hesitation. Colour, sound and heat, he says, are in the object only motions, and in us only appearances¹⁷. Pascal, in a passing remark, notes that excessive heat or cold is not so much perceived as suffered¹⁸. The remark hints that some qualities are better described as things undergone than as features of the world.

It is Berkeley who carries the argument through systematically, in the Three Dialogues between Hylas and Philonous. He begins with heat. Philonous asks whether real existence can be granted to some degrees of heat and not to others¹⁹. Hylas tries to hold that intense heat, which is a pain, exists only in the mind, while lesser degrees may inhere in bodies²⁰. Philonous denies that any degree of heat or cold can exist in an unperceiving body²¹. Hylas concedes, and Philonous extends the conclusion to tastes and the other qualities²². Sweetness, bitterness and odours, as perceived, are pleasures or pains and so cannot exist in senseless things. Hylas proposes to distinguish the quality as perceived from the quality as inherent, and this is rejected²³.

Sound gets the same treatment. Hylas suggests that “real” sound is a motion in the air. Philonous replies that loudness and sweetness cannot belong to a motion, so that the sound we hear and the motion physics describes are two different things^24,25. Colours, as perceived, are sensations in a mind, and in themselves only the motions of insensible particles²⁶. Hobbes and the physicists had used the language of motion to place the real quality outside us. Berkeley uses the same language to show that what is outside, on their account, is not the quality at all.

The arguments that carry most weight are those from relativity. Colours seen under the microscope differ from those seen by the naked eye, so the colours of ordinary sight are only apparent²⁷. Colours vary with the eye, the distance, the light and the prism, so that none can claim to be the true inherent colour of the object²⁸.

The decisive step is to turn these arguments against the primary qualities. Hylas has admitted that the secondary qualities depend on mind, and Philonous presses the same reasoning on extension, figure, solidity and motion²⁹. Extension and figure vary with the perceiver and the distance just as colour does^30,31. Hardness and resistance are relative to the senses that feel them. And to deny extension is to deny motion, solidity and gravity with it³². Hylas falls back on absolute extension and motion, abstracted from every particular size and speed. Philonous finds this abstraction empty³³. Primary qualities cannot even be conceived apart from secondary ones, and so they fall with them³⁴. In the end Hylas grants that no sensible quality can exist in an unperceiving substance, so that matter has neither figure nor motion³⁵.

Hume, in the Enquiry concerning Human Understanding, presents the same result as a sceptical outcome rather than a triumph. If the sensible qualities are merely secondary and exist in the mind, then extension and solidity must go too. What remains of matter is an unknown, inexplicable something³⁶. Berkeley and Hume reach the same point, but Hume draws a darker conclusion from it.

The dispute naturally passes into a question about substance. The traditional view, which Hylas defends, treats qualities as modes that need a support³⁷. Extension, for instance, is a mode supposedly upheld by matter³⁸. Berkeley answers that sensible things are nothing but combinations of sensible qualities; take the qualities away and nothing sensible remains³⁹. Corporeal substance proves to be nothing distinct from them⁴⁰. The cherry is its softness, moisture, redness and tartness⁴¹. Since each quality singly cannot exist without mind, neither can their combination⁴². Sensible qualities are ideas, passive and inert⁴³, and colour, figure and hardness are neither the real natures of things nor like them⁴⁴. The ancient distinction between fire and the heat it has¹ is not refined but dissolved: there is no bearer behind the qualities.

The irony of the controversy is that Berkeley claims common sense for his side. Philonous insists that on his view colour and heat are really on the objects: snow is white and fire hot. It is the materialist, he says, who denies this⁴⁵. The plain man and the idealist agree that the cherry is red. They part only on what being red requires. Burke appeals to a different kind of common sense when he holds that hot, cold, hard and soft are perceived alike by all men⁴⁶. His interest is not the metaphysics of the quality but its uniformity across perceivers, which he needs as a foundation for a standard of taste. Berkeley’s relativity arguments and Burke’s claim of uniformity are not strictly contradictory. Berkeley stresses variation with circumstance and instrument, Burke agreement among normal perceivers. Still, they pull in opposite directions.

A further question is what qualities reveal. Hume’s example is bread. Its colour, consistency and other sensible qualities disclose nothing of the secret powers that fit it to nourish the body⁴⁷. No connection between those qualities and those powers can be discovered by reason; experience alone links them⁴⁸. Sensible qualities are surfaces, and their bond with causal power is customary, not perceived. Voltaire’s Newtonian attraction is a quality defended because its effects are manifest⁵. Hume’s point cuts deeper: even manifest qualities do not show the power behind them.

Aesthetics gives sensible qualities a new role. Burke builds his theory of the beautiful and the sublime on them. Smoothness is a quality constantly found in beautiful objects⁴⁹. Mild colours, such as light greens, soft blues and pinks, belong to beauty⁵⁰. Dark and gloomy colours serve the sublime, while cheerful or gaudy ones are unfit for grand images⁵¹. Strength is awful and majestic, delicacy amiable⁵². Burke draws these together into seven sensible qualities that constitute beauty⁵³. He even gives sweetness a corpuscular explanation in the shape and size of particles, holding that insipid oil and water are slightly sweet⁵⁴. For Burke beauty is caused by qualities in bodies acting on uniform human senses.

Hume’s essay on taste answers him in effect. Beauty and deformity, like sweet and bitter, are not qualities in objects but belong to sentiment⁵⁵. Hume’s analogy assumes what Berkeley had argued, that taste qualities reside in feeling. Once that is granted, beauty goes the same way. Goethe, writing from the painter’s practice rather than from theory, speaks of warm and cold colours, and of colours that express nearness or distance through felt contrasts⁵⁶. Here colour is valued for what it does to the beholder. That fits Hume’s sentiment better than Burke’s objective causes, without forcing a choice between them.

Finally, the Bhagavad-Gita uses the word “quality” in a sense far from the Western dispute. Its three qualities of Nature, Sattwa, Rajas and Tamas, rendered as goodness, passion and ignorance, are not sensible features of bodies. They are forces that bind the changeless spirit in flesh⁵⁷. They classify foods, rites and forms of worship⁵⁸, and they divide knowledge, action and the agent himself⁵⁹. Quality here is moral and spiritual, a principle of bondage from which liberation is sought. The Western debate asks whether qualities are in things or in minds. The Gita treats them as pervading both and as something to be transcended.

Several questions remain open across these books. The scientists treat colour as a real disposition of bodies and light. The idealist treats it as a sensation; this does not refute the physicists, but it moves the name to another thing. It is still unsettled whether the primary qualities are more secure than the secondary, as the corpuscular physics assumed, or fall with them, as Berkeley and Hume maintained. It is also unsettled whether beauty is grounded in qualities perceived alike by all, as Burke held, or is a sentiment like sweet and bitter, as Hume held. Smith’s remark that quality is a very disputable matter⁸ was made about cloth, but it describes the whole idea.