Relation

Relation is the most pervasive and the least visible of ideas. Every comparison we make, every judgment that one thing is larger, earlier, likelier or more beautiful than another, rests on it. Under this heading fall likeness and difference, order and proportion, kinship and descent, cause and effect insofar as they bind one thing to another. The idea is a great one for these books because it does not belong to a single discipline. A dialogue on the immortality of the soul turns on it. So do a treatise on human understanding, a theory of the origin of species, and an essay on what a poet does. The persistent question is whether relations lie in things themselves or arise only when a mind sets things side by side. That question runs beneath them all, and the authors answer it differently according to their purposes.

The oldest form of the problem appears in Plato. Socrates observes that Simmias is said to be great when compared with Socrates and small when compared with Phaedo. Greatness and smallness, then, are not simply in Simmias; they belong to him only by comparison with others¹. The observation troubles any account of things as possessing fixed properties, for the same man bears contrary predicates at once. Later tradition gave such predicates a place among the highest kinds of being. Milton, in a college exercise, names Relation as one of the Predicaments, the categories under which whatever is may be said². If relation is a category, it is a genuine way of being, not a mere trick of language. Yet the very relativity Plato noticed tempts some thinkers to dissolve other qualities into it. Burke resists this move. He rejects the view that pleasure and pain are nothing but relations that exist only by contrast with each other. He holds them to be positive in their own nature³. The quarrel is instructive. Some things are evidently relative, as great and small are. But the claim that a thing is “merely” relative is itself something to be argued, not assumed.

If relations are not simply seen, they must be made out by some act of the mind. Rousseau states the point with unusual sharpness. In the Savoyard Vicar’s profession, he distinguishes between seeing two objects and perceiving their relations, their difference or their number. The first is sensation; the second is comparison, and comparison is an activity of the mind, not a passive reception⁴. In his discourse on inequality, Rousseau traces the origin of such ideas historically. Primitive men, by repeated dealings with the things around them, came to form notions of relation such as great and little, strong and weak⁵. The two passages fit together. The capacity to compare belongs to the mind, but experience supplies the occasions on which it is exercised. Marcus Aurelius, writing as a moralist, turns comparison into a discipline. He advises us to judge things by all their parts taken together rather than by a single striking feature⁶. A false comparison, on this view, is a failure to see the whole.

Hume carries the inquiry into the workings of thought itself. He reduces the association of ideas to three relations: resemblance, contiguity in time or place, and cause and effect. These bind our thoughts into regular trains rather than leaving them to wander at random⁷. Relation, for Hume, is the principle of mental order. He also argues that these relations give liveliness to ideas. A present impression, joined to an idea that resembles it, makes that idea more vivid⁸. Contiguity and causation work the same way: nearness to home revives thoughts of it, and the sight of a friend’s son brings the absent friend more strongly to mind⁹. Of the three relations, cause and effect matters most to know, since all reasoning about matters of fact depends on it. Yet Hume confesses that our ideas of this relation are imperfect¹⁰. Here the question of whether relations are real or mind-made becomes acute. The relation on which all practical inference rests is precisely the one whose ground in things we cannot clearly grasp.

Against this analytical caution stands a long tradition that sees the world as a web of real relations, whatever the mind contributes. Marcus Aurelius holds that existing things are arranged harmoniously and bear a wonderful relationship to one another¹¹. Augustine finds that creatures fit with their proper places and seasons. In his ordering, the higher a creature stands, the more it resembles God¹². Fitness and likeness to a source thus become marks of rank in the order of being. Pascal sees the same interconnection but draws from it a lesson of humility. The parts of the world are so related and linked that one cannot be known without knowing the others, so that knowledge of any part requires knowledge of the whole¹³. Even our own magnitude is relational. Our body is imperceptible compared with the universe, yet a colossus compared with the nothing below it¹⁴. Pascal thus extends Plato’s point about Simmias to the human condition as a whole. Emerson, by contrast, finds the linkage of things a ground of confidence. Things are so related, he says, that from one object the parts and properties of any other may be predicted¹⁵. He speaks of infinite relations, so like and so unlike, many and yet one¹⁶. Pascal and Emerson agree that everything is connected. They part on whether this connection puts knowledge within our reach or forever beyond it.

The natural sciences take up the interconnection of things in a more specific form. Harvey, tracing the motion of the heart, attends to the way the movements of auricle and ventricle are kept in harmony and rhythm. Each part’s action is timed in relation to the other’s¹⁷. Faraday states the program of a whole science in relational terms. His aim is to comprehend the mutual relation of the forces of matter and the conversion of one into another¹⁸. Where the older harmony was a matter of fitting order, Faraday’s relations are dynamic. Heat, motion and the other forces are related because they pass into one another. The Stoic intuition of a connected world survives, but it now becomes a question for experiment.

The same sense of mutual dependence governs human affairs. Marcus Aurelius holds that men are made for one another. This relation, he says, should govern how we respond when someone offends us, for to resent a fellow member of the whole is to forget what we are¹⁹. Emerson gives social relation a more economic cast. Every transaction of benefit and debt alters the relation of superiority and inferiority between neighbors, so that to receive without returning is to fall beneath the giver²⁰. In both, a relation is not a neutral fact. It carries an obligation, and conduct is measured by fidelity to it.

The richest single treatment of relation among living things is Darwin’s, and it transforms the older notion of likeness. Naturalists had long grouped organisms by “affinity,” a word suggesting resemblance and kinship at once. Darwin gives the word a literal meaning. The degrees of affinity among descendants depend on how recently they branched from common ancestors²¹. Species that have changed little hold circuitous affinities, intermediate between the types of the groups that diverged from them²². Degrees of likeness and distinctness among whole families can be reasoned out from common descent and from the number of characters in which they differ²³. Darwin’s governing image is a family. The affinities of organisms resemble the blood relationships among the kindred of a noble family, which can be traced only by a genealogical tree²⁴. Yet he also notes a subtlety: descendants may be related in blood to the same degree and still differ widely in form. Classificatory rank therefore expresses degrees of difference, not degrees of descent alone²⁵. Relation by descent and relation by likeness, which the word affinity had joined, are here distinguished and then reconnected.

Darwin’s account also reveals the shape such relations take. Organic beings are related in degrees, grouped in clusters subordinate to other clusters²⁶. Systematic affinity is meant to express every kind of resemblance and dissimilarity among them²⁷. For that very reason the pattern cannot be set out in a linear series or even on a flat diagram²⁸. The ancient image of a single ladder of beings, still visible in Augustine’s ranking of creatures by likeness to God¹², gives way to a branching figure of many dimensions. Darwin adds that relations among organisms are not only genealogical. Every being’s structure is related, often in hidden ways, to all the other beings with which it competes²⁹. The species of a large genus cluster around one another like satellites, related to each other as varieties are³⁰. Resemblance between species does not strictly match the ease with which they can be crossed³¹. One kind of relation, then, cannot simply be read off from another. The same comparative habit governs his geology. In the Beagle narrative, he argues that barrier reefs and atolls are alike in structure, so that an encircled island is an atoll with land still standing within³². The three classes of reef, he concludes, are essentially alike and pass into one another by gradations³³. Recognizing likeness of structure becomes a means of discovering a common history.

When the inquiry turns to art, relation appears as proportion. Pascal remarks that things made after the same model bear a perfect relation to one another, even when they are of different kinds³⁴. Burke takes up the classical doctrine that beauty consists in proportion. He grants that proportion arises from the relation of parts to one another and to the whole³⁵. He then denies that this is what makes things beautiful. He finds no proportion between the stalk and the flower-head, nor among the parts of the orange-tree, yet these please³⁶. What usually passes for proportion, he argues, is really the suitableness of means to ends. Measures related to nothing at all lose whatever force they seemed to have³⁷. Burke’s argument is another case of disputing what kind of relation is at stake. Proportion is still a relation, but he locates it in the fit between a thing and its purpose, not in numerical ratio among its parts.

Poetry, on several accounts, consists in finding relations that ordinary perception misses. Johnson defines the simile precisely. A simile finds likeness between dissimilar things; to note the likeness of things already similar is mere exemplification³⁸. Wordsworth makes the principle still more fundamental. The mind’s pleasure in perceiving similitude in dissimilitude is, he holds, the source of the pleasure we take in metre. It is also the source of taste and even of our moral feelings³⁹. In his discussion of imagination, he shows images placed together modifying one another. The stone, the sea-beast and the old man coalesce in a just comparison until each takes on qualities of the others⁴⁰. Shelley goes furthest. Poets, he says, mark before unapprehended relations of things. He cites the similitudes of Bacon as tracings of the very order of nature⁴¹. Swift’s advice to a young poet calls the bringing of things with no conformity in nature into likeness by the name of creation⁴². The phrase, set beside Shelley’s, poses the old question again. Does the poet discover relations that are really there, or does he make them? Shelley leans toward discovery. Swift’s word “creation” points toward invention, and his letter of advice, as its title suggests, may intend the word with some irony.

The sciences, finally, show relation in its most exact and its most suggestive forms. Descartes observes that all the mathematical sciences, however different their objects, agree in considering only the relations or proportions found among those objects⁴³. Proportion, which Burke questioned as a ground of beauty, here becomes the very substance of a discipline. Beyond mathematics, analogy serves explanation. Adam Smith compares money to fixed capital and notes their resemblance. He also reasons about the capital of a whole society by comparison with that of an individual⁴⁴. Lyell compares the local alternation of earthquakes and repose to the alternation of the seasons, which do not occur everywhere at once⁴⁵. He likens the extinction and appearance of species to the deaths and births recorded in a census taken province by province⁴⁶. Kelvin draws an analogy between the vibrations of sound and those of light, comparing their frequencies and proportions⁴⁷. In these hands, comparison is a working instrument. It carries what is understood in one domain over into another.

What these texts leave unsettled is the question with which they began. Plato’s relative predicates¹ and Rousseau’s insistence that comparison is the mind’s own act⁴ suggest that relations are at least partly made by the knower. Hume’s confession that the most important relation, cause and effect, is imperfectly understood¹⁰ leaves its reality in doubt. Yet Faraday’s conversion of forces¹⁸, Darwin’s genealogy of living things²⁴ and Emerson’s predictive web¹⁵ all treat relations as the very structure of what exists. The poets add a third possibility: that the mind, in comparing, may bring to light relations that are both real and hitherto unseen^41,39. Whether likeness is found or made, and whether order belongs to the world or to the mind that perceives it, remains an open question in these books.