Chapter III

To attempt to explain the nature of matter, or heat, or light, the mechanism by which they act, or the method by which their energy is translated into sensation and thought, this, however, is to pass into the realm of metaphysics, or what Newton excellently called hypothesis. All such speculations are, at best, transitory, and, instead of predicting new lines of work, they lag behind the sure and steady advance of experimentation; they are constantly being revised to explain new phenomena after they are discovered. A convincing illustration of this criticism can be found in the history of the hypotheses of the nature of light. Physicists commonly assert that the corpuscular hypothesis retarded the advance of the subject of light for a century; their answer was to replace it by an equally metaphysical hypothesis of mechanical waves in an æther. After incessantly patching up this new conception during the next century, they are again returning to a corpuscular hypothesis, even more metaphysical and incomprehensible than its prototype. It seems impossible for us to learn that the trouble does not arise from the weakness of any particular variety, but lies in the nature of hypothesis, itself. We have created fictitious æthers, atoms, and electrons which bear no resemblance to sensible bodies; light is alternately a stream of corpuscles, or waves, or quanta of energy, or even a mathematical symbol; space is declared to be impenetrable except along certain curves; and time is confused with space. What one age proposes as a great advance is flung aside by the next which makes a new hypothesis whose only fate is to be rejected. So far have these speculations been carried that the dogma is seriously maintained that a false scientific hypothesis is valuable because in some mysterious way it leads to the discovery of truth.

As we have advanced in sober experimental science, these hypotheses have become more and more abstruse and more and more dogmatic until the most recent of these dreamers, Whitehead, Eddington, Einstein, have pictured a phantasmagoria, instead of a world, as non-sensical as the hallucinations of the mediæval monk driven mad by the fevers of asceticism.

Such models of the structure of matter may, indeed, be useful to give substance to our thought and a language for our ideas. They have something of the same sort of relation to real objects that portraits do to living persons. But there is this important point to be remembered. A skilful painter has seen and studied the person and can make so faithful a likeness as to create the illusion of reality. But the man of science is attempting to picture things which can never be seen, for atoms lie in the realm of the infinitely small, whose very existence is problematical. Models of atoms, of æthers, or of space have about the same degree of authenticity as the posthumous portrait of a person whom no one then alive had ever seen. Men of science are too prone to confuse the thing and the model in their own minds, and they have certainly been so careless in their teaching that even very highly educated laymen accept these hypotheses as facts. Is it not true that the world pretty generally takes the hypothetical explanation of gravitation by Einstein, which involves the concept of a fictitious space of more than three dimensions and the fusion of time with space, to be equally as scientific, and therefore equally as true, as the experimental law of the attraction of bodies? Do not many accept as a demonstrated fact one or another of the many hypotheses advanced by biologists to explain the cause of the observed variations in species? And having failed to distinguish between scientific fact and fiction, we have incorporated this mass of speculation into our philosophy of life and especially into our religion. We are worse confused than the Deists of the eighteenth century who believed that the mind of God could be defined by learning the facts and laws of Nature; we now propose that the intellectual and spiritual attributes of Man be framed in the hypotheses of dogmatic Science.

That the scientific method, as evolved from physics and chemistry, is not applicable to the problems of life has been the settled conviction of virtually all the investigators in those sciences. In fact, in order to achieve their results they have had to assume that life is a perturbation which cannot be included in a mechanical and mathematical world, and that so far as possible sense-perceptions must be excluded as criteria of laws. However, it has not been so clear to many of them that the mechanical method imposes definite, and rather narrow, limitations even upon the study of physical and chemical problems. These limitations were clearly defined in the seventeenth century during the protracted controversy between Newton on the one side, and Hooke and Huygens on the other, as to the nature of light and the _modus operandi_, or mechanism, of its transmission. The question involved was clear-cut; and it will pay to discuss it in some detail because it settled once for all, I think, the distinction between science and humanism.

Theoretical physics, from the very beginning, has been a synthesis of phenomena in terms of mechanics; that is, in terms of substance and motion. For example, the physical properties of heat, sound, and light are expressed by the same mathematical formulæ which express the motion of a wave in water. To distinguish between them, we assign different names to the substances involved, as a molecule of air, a corpuscle of light, or an æther. But whatever names we may give to them, or however we may try to distinguish them, we assign to all of them the common attribute of mass, or inertia, which is the only essential coefficient in a mechanical equation. And we use for all these different phenomena the same formula of motion, the quotient of the distance by the time. These quantities, mass and motion, when combined give us the law of mechanical energy, and our synthesis rests on the single fact that heat, sound, and light may be changed into mechanical motion, and may be produced by it. This energy is then their common and mutable factor.

But the objective phenomena of heat, light, and sound are cognisable to us through three separate sense-organs and are perceived as temperature, sight, and tone. These sensations are fundamentally different and, in fact, to confuse any of them with another is one of the surest indications of insanity. Thus the world as depicted by the physicist does not correspond with our world of sensation; nor does he attempt to do more than to discuss a restricted set of attributes, and not even those which really distinguish heat, light, etc., as such.

Newton, in his earliest published work, made evident this essential difference between the fields of physics and psychology. By means of a prism he refracted a beam of white sunlight into a continuous spectrum. He then placed a screen, containing a narrow slit, behind the prism in such a way as to permit only a very thin ray from the spectrum to pass on, and through, a second prism fastened parallel to the first prism. (I call it a homogeneous light ray to distinguish it from its psychological analogue, colour.) No matter what portion of the spectrum was used for the second prism, there was no further change of colour; the ray merely suffered a second angular deviation equal to that produced by the first refraction. He also recombined the whole spectrum by a reversed prism and obtained a single ray parallel to the original ray and pure white in colour. As a result of his experiments, he announced the following law: a primary ray of light is one which has a definite and specific angle of refraction by a prism, and each such primary ray is, to the eye, a primary colour. White is therefore a mixture of an indefinitely large number of primary rays, each possessing a different angle of deviation when passed through a prism; and when so separated each primary ray is seen by the eye as a primary colour.

The experiments of Newton were accepted as correct by Huygens and Hooke, probably the two most eminent physicists of the time. But they objected to his definition of a primary colour and to his conclusions. They had found previously, by their own experiments, that certain pairs of complementary colours, such as a certain red and a certain blue, gave to the eye the same sensation of white as did clear sunlight. They had defined them as the two primary colours which, by different proportions of mixture, would produce all other colours, including white. They therefore objected that it was unnecessary and cumbersome to assume an infinite number of primary rays when two were quite sufficient. By no process of reasoning could these two opinions be either reconciled or controverted. They involved fundamentally different criteria. White produced by the combination of a continuous spectrum and the white produced by a combination of red and blue were one and the same to Hooke and Huygens because their criterion of identity was the sensation of sight, and it must be the same for all psychologists who deal with subjective light. To Newton, the two whites were altogether different. The one examined by a prism gives a continuous spectrum, and the other gives two separated bands of blue and red. What, then, to the physicist is a fundamental dissimilarity is to the psychologist complete identity. How then can psychological sensations be studied by physical methods?

To show that this is not an isolated case, but that this gulf runs between the entire fields of physics and psychology, I can give an artificial example. While I deprecate the pseudo-scientific pictures, now fashionable, of the state of prehistoric man and of the condition of the earth before its habitability, I am able to imagine a world in which the eye had never developed, so that all life was blind. I am sure the word colour would never have been coined in such a world and that there could be no psychology of sight, but I also know that the blind race could develop a physical science of light because very many of its phenomena can be, and are now exclusively, studied by such apparatus as thermometers and electric galvanometers which can be read by touch. Or, to cite an everyday example, is not the mere fact, that the sensation produced by pepper on the tongue cannot be distinguished from that of heat, sufficient to make us hesitate before trying to study the sensations objectively, to synthesise the objective and subjective worlds, or to try to investigate them by the same method?

The history of physics, since the time of Maxwell, shows a record of vain efforts to reconstruct a materialistic monism. These attempts have failed because they involved a supposititious æther and atom which could no longer satisfy the growing body of experimental facts about radiant energy. After Maxwell predicted the existence of electro-magnetic radiation, an æther or atom possessing the ordinary attributes of matter became an absurdity.

But our childish, or at least youthful, reluctance to admit our limitations is so great that we proceeded to repeat the hypothetical method once more by substituting an energiastic monism. Unmindful of Pascal’s dictum that man cannot investigate the world of either the infinitely small or the infinitely large, we are replacing a material atom and æther by Planck’s hypothesis of discrete and disembodied _quanta_, or atoms, of energy. Already there have arisen four insuperable difficulties.

The hypothesis affirms action without specifying something to act, unless the word _energy_ is given all the physical attributes of matter. In which case a _quantum_ of radiant energy is merely our old friend, a corpuscle of light, masquerading under a new name. Again, it substitutes the principle of discontinuity of action for continuity, and one is puzzled to know from what the _quantum_ originates and in what it ends. And again, it creates the dilemma that light is simultaneously corpuscular and vibrational, since without the latter quality none of the phenomena of interference is explicable. Lastly, it drifts into a pure philosophy of idealism.

My discussion would not be complete without a reference to the theory of relativity. It is significant that the earliest serious critique of Newtonian physics was made by Bishop Berkeley. With the greatest ingenuity and skill, he pointed out that objects can become known to us only _by_ the mind and that since light, sound, and motion are interpreted by the mind as essentially different, they cannot be synthesised by any experimental and objective process. So far Berkeley’s critique is thoroughly valid. He proceeded, however, to make the _non-sequitur_ that objects exist only _in_ the mind. If we accept this postulate, the logic of idealism is irrefutable; few, however, will accept it. Idealism fails because it ignores brute fact, and we accept the answer of Dr. Johnson who made his objection by merely kicking a large stone in his path.

Einstein also began with a critique of Newtonian dynamics to prove that the conclusions we can draw from electrodynamics are as limited and as relative as those from mechanics. From this denial of our ability to obtain real or absolute knowledge he, like Berkeley, has proceeded to construct a positive philosophy of the absolute. Relativity, as it has now been interpreted by such disciples as Whitehead and Eddington, is merely idealism under a new guise. The objective world of sensation and experience is illusion, and truth exists only in a set of subjective mathematical formulæ of cosmic _events_. The relativists openly rejoice that mathematics has come into its own kingdom and is no longer to be the handmaiden of physics, no longer to be restricted by the limitations of the sense-perceptions. Euclidean geometry, which is limited to the three dimensions of tactual space, has been replaced by a geometry of hyper-space, the properties of which no one can be cognisant of. Subjective time is eliminated, and objective time is conflated with space. They, too, deny the validity of the senses, as did the mediæval schoolman, and picture a topsy-turvy world. They are labouring under the delusion that the limitations of logic can be avoided by the simple substitution of mathematical symbols for words, forgetting that mathematical symbols are as meaningless as words when they are detached from facts. They fail to see that the equation is but a form of the syllogism. One can trace all through their argument the old and familiar fallacy of the ambiguous middle. They are quite reckless, as it suits their convenience, in confusing physical space of three dimensions with mathematical space of an unlimited number; neither do they distinguish time as a subjective sequence of events from time as a measurable component of velocity. The relativists are as rash as those sociologists who see a real connection between physical energy of motion and mental energy of thought and so deceive themselves with the notion that they are scientific.

A note of uncertainty is beginning to show itself, however, for thoughtful physicists are seeing the _impasse_ into which their unbridled hypotheses have led them. Abstruse mathematical analysis is again proving to us, what Pascal, Newton, Lagrange, and philosophy had demonstrated in a simpler way, that the mechanistic method can, at best, only picture an objective world as it seems to us, and not as it is. As a recent physicist confesses: “The physicist thus finds himself in a world from which the bottom has dropped clean out; as he penetrates deeper and deeper it eludes him and fades away by the highly unsportsmanlike device of just becoming meaningless. No refinement of measurement will avail to carry him beyond the portals of this shadowy domain which he cannot even mention without logical inconsistency. A _bound_ is thus forever set to the curiosity of the physicist. What is more, the mere existence of this bound means that he must give up his most cherished convictions and faith. The world is not a world of reason, understandable by the intellect of man, but as we penetrate ever deeper, the very law of cause and effect, which we had thought to be a formula to which we could force God himself to subscribe, ceases to have meaning.”[1] The answer to this naïve confession is simple enough: there never was a _bottom_ to his hypothetical world, as he could have foreseen if he had acquainted himself with the warning of the more profound men of science, philosophers, and humanists.

The writer adds that this failure, now proved, “must forever keep the physicist humble.” But there is no cause for him to think lowly of himself for what he has accomplished and for what he may achieve. He should, rather, be modest and restrict himself to what can be done legitimately by the scientific method. I fear, however, that in spite of such occasional confessions, the physicists are neither humble nor modest, but are merely bewildered. The false pretensions of science must be wholly abandoned, and the problems of our destiny be examined by a wise judgment drawn from human experience, before we can hope for a sane and humanistic philosophy.

FOOTNOTES

[1] “The New Vision of Science,” by Professor P. W. Bridgman, _Harper’s Magazine_, 1929.

_Humanism: An Essay at Definition_

IRVING BABBITT