Theory and practice in the latest science are still allied, otherwise neither of them would prosper as it does; but each has taken a leap in its own direction. The distance between them has become greater than the naked eye can measure, and each of them in itself has become unintelligible. We roll and fly at dizzy speeds, and hear at incredible distances; at the same time we imagine and calculate to incredible depths. The technique of science, like that of industry, has become a thing in itself; the one veils its object, which is nature, as the other defeats its purpose, which is happiness. Science often seems to be less the study of things than the study of science. It is now more scholastic than philosophy ever was. We are invited to conceive organisms within organisms, so minute, so free, and so dynamic, that the heart of matter seems to explode into an endless discharge of fireworks, or a mathematical nightmare realised in a thousand places at once, and become the substance of the world. What is even more remarkable—for the notion of infinite organisation has been familiar to the learned at least since the time of Leibniz—the theatre of science is transformed no less than the actors and the play. The upright walls of space, the steady tread of time, begin to fail us; they bend now so obligingly to our perspectives that we no longer seem to travel through them, but to carry them with us, shooting them out or weaving them about us according to some native fatality, which is left unexplained. We seem to have reverted in some sense from Copernicus to Ptolemy: except that the centre is now occupied, not by the solid earth, but by any geometrical point chosen for the origin of calculation. Time, too, is not measured by the sun or stars, but by any "clock"—that is, by any recurrent rhythm taken as a standard of comparison. It would seem that the existence and energy of each chosen centre, as well as its career and encounters, hang on the collateral existence of other centres of force, among which it must wend its way: yet the only witness to their presence, and the only known property of their substance, is their "radio-activity", or the physical light which they shed. Light, in its physical being, is accordingly the measure of all things in this new philosophy: and if we ask ourselves why this element should have been preferred, the answer is not far to seek. Light is the only medium through which very remote or very minute particles of matter can be revealed to science. Whatever the nature of things may be intrinsically, science must accordingly express the universe in terms of light.
These reforms have come from within: they are triumphs of method. We make an evident advance in logic, and in that parsimony which is dear to philosophers (though not to nature), if we refuse to assign given terms and relations to any prior medium, such as absolute time or space, which cannot be given with them. Observable spaces and times, like the facts observed in them, are given separately and in a desultory fashion. Initially, then, there are as many spaces and times as there are observers, or rather observations; these are the specious times and spaces of dreams, of sensuous life, and of romantic biography. Each is centred here and now, and stretched outwards, forward, and back, as far as imagination has the strength to project it. Then, when objects and events have been posited as self-existent, and when a "clock" and a system of co-ordinates have been established for measuring them, a single mathematical space and time may be deployed about them, conceived to contain all things, and to supply them with their respective places and dates. This gives us the cosmos of classical physics. But this system involves the uncritical notion of light and matter travelling through media previously existing, and being carried down, like a boat drifting down stream, by a flowing time which has a pace of its own, and imposes it on all existence. In reality, each "clock" and each landscape is self-centred and initially absolute: its time and space are irrelevant to those of any other landscape or "clock", unless the objects or events revealed there, being posited as self-existent, actually coincide with those revealed also in another landscape, or dated by another "clock". It is only by travelling along its own path at its own rate that experience or light can ever reach a point lying on another path also, so that two observations, and two measures, may coincide at their ultimate terms, their starting-points or their ends. Positions are therefore not independent of the journey which terminates in them, and thereby individuates them; and dates are not independent of the events which distinguish them. The flux of existence comes first: matter and light distend time by their pulses, they distend space by their deployments.
This, if I understand it, is one half the new theory; the other half is not less acceptable. Newton had described motion as a result of two principles: the first, inertia, was supposed to be inherent in bodies; the second, gravity, was incidental to their co-existence. Yet inherent inertia can only be observed relatively: it makes no difference to me whether I am said to be moving at a great speed or absolutely at rest, if I am not jolted or breathless, and if my felt environment does not change. Inertia, or weight, in so far as it denotes something intrinsic, seems to be but another name for substance or the principle of existence: in so far as it denotes the first law of motion, it seems to be relative to an environment. It would therefore be preferable to combine inertia and attraction in a single formula, expressing the behaviour of bodies towards one another in all their conjunctions, without introducing any inherent forces or absolute measures. This seems to have been done by Einstein, or at least impressively suggested: and it has been found that the new calculations correspond to certain delicate observations more accurately than the old.
This revolution in science seems, then, to be perfectly legal, and ought to be welcomed; yet only under one important moral condition, and with a paradoxical result. The moral condition is that the pride of science should turn into humility, that it should no longer imagine that it is laying bare the intrinsic nature of things. And the paradoxical result is this: that the forms of science are optional, like various languages or methods of notation. One may be more convenient or subtle than another, according to the place, senses, interests, and scope of the explorer; a reform in science may render the old theories antiquated, like the habit of wearing togas, or of going naked; but it cannot render them false, or itself true. Science, when it is more than the gossip of adventure or of experiment, yields practical assurances couched in symbolic terms, but no ultimate insight: so that the intellectual vacancy of the expert, which I was deriding, is a sort of warrant of his solidity. It is rather when the expert prophesies, when he propounds a new philosophy founded on his latest experiments, that we may justly smile at his system, and wait for the next.
Self-knowledge—and the new science is full of self-knowledge—is a great liberator: if perhaps it imposes some retrenchment, essentially it revives courage. Then at last we see what we are and what we can do. The spirit can abandon its vain commitments and false pretensions, like a young man free at last to throw off his clothes and run naked along the sands. Intelligence is never gayer, never surer, than when it is strictly formal, satisfied with the evidence of its materials, as with the lights of jewels, and filled with mounting speculations, as with a sort of laughter. If all the arts aspire to the condition of music, all the sciences aspire to the condition of mathematics. Their logic is their spontaneous and intelligible side: and while they differ from mathematics and from one another in being directed in the first instance upon various unintelligible existing objects, yet as they advance, they unite: because they are everywhere striving to discover in those miscellaneous objects some intelligible order and method. And as the emotion of the pure artist, whatever may be his materials, lies in finding in them some formal harmony or imposing it upon them, so the interest of the scientific mind, in so far as it is free and purely intellectual, lies in tracing their formal pattern. The mathematician can afford to leave to his clients, the engineers, or perhaps the popular philosophers, the emotion of belief: for himself he keeps the lyrical pleasure of metre and of evolving equations: and it is a pleasant surprise to him, and an added problem, if he finds that the arts can use his calculations, or that the senses can verify them; much as if a composer found that the sailors could heave better when singing his songs.
Yet such independence, however glorious inwardly, cannot help diminishing the prestige of the arts in the world. If science misled us before, when it was full of clearness and confidence, how shall we trust it now that it is all mystery and paradox? If classical physics needed this fundamental revision, near to experience and fruitful as it was, what revision will not romantic physics require? Nor is the future alone insecure: even now the prophets hardly understand one another, or perhaps themselves; and some of them interlard their science with the most dubious metaphysics. Naturally the enemies of science have not been slow to seize this opportunity: the soft-hearted, the muddle-headed, the superstitious are all raising their voices, no longer in desperate resistance to science, but hopefully, and in its name. Science, they tell us, is no longer hostile to religion, or to divination of any sort. Indeed, divination is a science too. Physics is no longer materialistic since space is now curved, and filled with an ether through which light travels at 300,000 kilometres per second—an immaterial rate: because if anything material ventured to move at that forbidden speed, it would be so flattened that it would cease to exist. Indeed, matter is now hardly needed at all; its place has been taken by radio-activity, and by electrons which dart and whirl with such miraculous swiftness, that occasionally, for no known reason, they can skip from orbit to orbit without traversing the intervening positions—an evident proof of free-will in them. Or if solids should still seem to be material, there are astral bodies as well which are immaterial although physical; and as to ether and electricity, they are the very substance of spirit. All this I find announced in newspapers and even in books as the breakdown of scientific materialism: and yet, when was materialism more arrant and barbarous than in these announcements? Something no doubt has broken down: but I am afraid it is rather the habit of thinking clearly and the power to discern the difference between material and spiritual things.
The latest revolution in science will probably not be the last. I do not know what internal difficulties, contradictions, or ominous obscurities may exist in the new theories, or what logical seeds of change, perhaps of radical change, might be discovered there by a competent critic. I base my expectation on two circumstances somewhat more external and visible to the lay mind. One circumstance is that the new theories seem to be affected, and partly inspired, by a particular philosophy, itself utterly insecure. This philosophy regards the point of view as controlling or even creating the object seen; in other words, it identifies the object with the experience or the knowledge of it: it is essentially a subjective, psychological, Protestant philosophy. The study of perspectives, which a severer critic might call illusions, is one of the most interesting and enlightening of studies, and for my own part I should be content to dwell almost exclusively in that poetic and moral atmosphere, in the realm of literature and of humanism. Yet I cannot help seeing that neither in logic nor in natural genesis can perspectives be the ultimate object of science, since a plurality of points of view, somehow comparable, must be assumed in the beginning, as well as common principles of projection, and ulterior points of contact or coincidence. Such assumptions, which must persist throughout, seem to presuppose an absolute system of nature behind all the relative systems of science.
The other circumstance which points to further revolutions is social. The new science is unintelligible to almost all of us; it can be tested only by very delicate observations and very difficult reasoning. We accept it on the authority of a few professors who themselves have accepted it with a contagious alacrity, as if caught in a whirlwind. It has sprung up mysteriously and mightily, like mysticism in a cloister or theology in a council: a Soviet of learned men has proclaimed it. Moreover, it is not merely a system among systems, but a movement among movements. A system, even when it has serious rivals, may be maintained for centuries as religions are maintained, institutionally; but a movement comes to an end; it is followed presently by a period of assimilation which transforms it, or by a movement in some other direction. I ask myself accordingly whether the condition of the world in the coming years will be favourable to refined and paradoxical science. The extension of education will have enabled the uneducated to pronounce upon everything. Will the patronage of capital and enterprise subsist, to encourage discovery and reward invention? Will a jealous and dogmatic democracy respect the unintelligible insight of the few? Will a perhaps starving democracy support materially its Soviet of seers? But let us suppose that no utilitarian fanaticism supervenes, and no intellectual surfeit or discouragement. May not the very profundity of the new science and its metaphysical affinities lead it to bolder developments, inscrutable to the public and incompatible with one another, like the gnostic sects of declining antiquity? Then perhaps that luminous modern thing which until recently was called science, in contrast to all personal philosophies, may cease to exist altogether, being petrified into routine in the practitioners, and fading in the professors into abstruse speculations.