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.