IF an inquiring microbe should ask me to explain what I know about the sun, he would understand part of my description. He could realize the distance almost as well as I can, because he is only a million times shorter than I am and could easily imagine his own length multiplied by that number. He could understand the heat of the sun about as well as I can, for his sensitiveness to heat is much the same as mine. I should find him an intelligent listener.
But when I began to tell him how the sun looks, he would give a disdainful wriggle and tell me to quit being mystical. In his mind there is nothing that corresponds to looks. For he has no sense of sight, no apparatus like an eye which can receive light rays and convert them into a feeling that he is acquainted with a distant object. Light rays do produce an effect on his consciousness, but only a vague, diffused feeling of discomfort. They do not create pictures in him. If I try to explain what they do to me — try to show by analogies what a picture of the sun is like — he will think that I have gone beyond common sense and am babbling metaphysics. It is not merely his ignorance that makes him unable to learn from me, but his unconsciousness of being ignorant.
So, in a similar way, if I could put a human inquiry about space to a seraph, and if he obligingly began to explain, I should soon find his talk intolerable.
For he would have to say something like this: ‘Space is the force which brings time closer to my mind. It makes a separation between time and matter, so that I can avoid matter and fly only in time. Don’t you see?’ This would not sound like common sense. I should be impatient of it, not so much because of my ignorance as because of my unconsciousness that I am utterly ignorant of what space can do for a seraph. I have never been conscious that space is a force. It does n’t make any more contact with my mind than light does with a microbe’s mind. Space, for me, is just emptiness; it is only a name for the fact that pieces of matter are not all together. I am powerless to imagine that space is something — a great force, a phase of matter that acts on the mind of a seraph and reveals to him a portion of the universe to which my senses can make no response. I can no more perceive my ignorance of space than an oyster can realize that he does not know what rainbows look like.
It is the human unawareness of time and space that recent science is struggling with. It has found a clue to them which was furnished by an experiment with light, and it is trying to follow the clue, gropingly and falteringly, by the use of mathematics. Science is not at all sure of what it is doing or where it is going, but it is keeping hold of the clue and tracing its unimaginable course to — somewhere, perhaps. We can see these mathematicians working in the bright sunshine, fumbling about where eyesight is of no avail. They have no sixth sense that tells them anything about time and space — any more than a microbe has a sense of sight. They can see, everywhere, out through unnumbered galaxies that are millions of light years away, but they are not able to feel the time and space that are directly perceived by a seraph. They are groping for some slight, indirect knowledge, reaching here and there in the light that can reveal nothing. Hence their occupation seems mystical, not to say ludicrous; for they are putting out mathematical feelers beyond their senses.
If we wish to understand what the physicists have been feeling for, during the past twenty years, we must first be assured that this most recent form of science is not different in purpose or nature from what it has always been. It is exactly the same sort of mental operation that Huxley described eighty years ago, in his address at St. Martin’s Hall ‘On the Educational Value of the Natural History Sciences’: —
Science is nothing but trained and organized common sense, differing from the latter only as a veteran may differ from a raw recruit. . . . The vast results obtained by science are won by no mystical faculties, by no mental processes, other than those which are practised by every one of us, in the humblest and meanest affairs of life.
. . . The man of science simply uses with scrupulous exactness the methods which we all, habitually and at every moment, use carelessly.
It was easier for Huxley to convince his audience of this truth in 1854 than it would be now. For during the past twenty years the scientists have discharged such a barrage of fanciful possibilities that they have not seemed to talk common sense. They have bewildered us with the free will of electrons, with a finite but unbounded universe, with expanding space, with space that would be destroyed by too much matter, with time that is only a phase of space, with matter that is only a form of energy, with the chance that a flame might turn water to ice, with the probability that a million monkeys leaping about on a million typewriters would reproduce the books in the British Museum. If Huxley were brought back to life in 1933 and, without any preparation, suddenly confronted with all those notions, he might well suspect that science had deserted its five senses and gone on a picnic with its fancies. He might naturally fear that common sense has become old-fashioned and that science is now a kaleidoscope of incredibilities.
But as soon as his first bewilderment was over he would recover his composure, ask for a cup of coffee, and request some professor at the Imperial College of Science to give him an account of how the weird things originated. He would not assume that science had gone crazy in the twentieth century, but would prepare himself to understand what its strange new language meant. The strangeness would not perturb him, for he would know that nothing recent and complicated could be essentially more mysterious than the oldest and simplest experience that primitive man had of the universe in which he found himself.
When an eye makes contact with a bull that is grazing on a hill a mile away, it gives us experience of a mystery so profound that anything proposed by relativity is simple in comparison. No philosopher or psychologist or physicist has the least understanding of what that contact is like: of what the distance is, or the motion is, or of what the correspondence is between the thing on the hill and the impression somewhere within a human skull. But we live unconscious of this deepest ignorance. We assume that of course the passage of a bull to a brain is a commonplace that may be taken for granted. Not till we hear of ‘a bull in the brain’ do we recognize anything that needs explaining.
Huxley was aware that the simplest and oldest mystery is the deepest one; and he would not expect the most fantastic discovery of twentieth-century science to be harder to comprehend. He might say to the professor: ‘Let’s put your free-will electrons and your typewriting monkeys to one side for the present. Begin at the beginning. Tell me what originated these quaint playthings of the intellect. For all their grotesqueness, I presume they are just phases of the same old common sense that I used to lecture about.’
And the professor might begin with a matter-of-fact narrative like the following.
The first inkling that a human being ever got of space — an element of the universe which our senses cannot perceive — was detected by an American professor of physics at the Case School of Applied Science in Cleveland, in 1887. His name was Albert Abraham Michelson. He was as hard-headed and non-mystical an experimenter as ever wore a dirty apron in a laboratory. He had completed an investigation with a set of mirrors and a big stone that was floated in a vat of mercury. There had been no philosophy about his work. His apparatus and his reasoning were so simple in principle that any freshman in the Case School could understand them. Every freshman, like every professor of physics in the world at that time, would have bet a hundred to one that the result of the experiment would be positive. But it was negative. The negative result was just as astonishing to Michelson as it was to everybody else. It was as puzzling as if he had found that a man can row upstream as fast as he can row downstream.
That way of describing the situation is a literal statement of what had happened. Until Michelson’s experiment was completed, the human mind had always known that when two speeds are added together they produce the sum of the speeds. If, for example, I am on an escalator which is taking me upstairs at the rate of four feet a second, and if I am in a hurry and add my walking speed of five feet a second to the speed of the escalator, I move upstairs at the rate of nine feet every second. A stop watch will prove that I actually do add the two speeds. Any boy can measure the addition of the speed of his rowing to the speed of a river current, and find that he moves ahead at the sum of the two speeds. If a man stands on the deck of a steamer and throws a baseball forward, the ball moves with the speed of the throw plus the speed of the steamer. Everybody knows that it does. Nobody can conceive that the sum of two motions is anything but the sum of them. Yet Michelson had found — if his measurements were correct — that something in his basement laboratory, impelled by two motions at once in the same direction, had the speed of only one motion.
The something was light. Michelson had measured the speeds of rays of light in many directions. His reasoning was this: If a light ray, traveling with its own proper speed, moves in the direction of the earth’s motion through space, it will have the sum of the speeds; if it moves in a direction opposite to the earth’s course, it will — like a man rowing upstream — have its speed diminished by the amount of the earth’s speed. What could be simpler or more certain? For measuring the speed of the light rays he had an instrument so sensitive that it would have detected differences far smaller than the earth’s motion around the sun would give. Thus he felt no doubt that by a series of measurements he could tell the direction of the earth’s movement through space. The speed would be highest when the light traveled in the same direction as the earth; it would be slowest when the light traveled in the direction opposite to the earth’s. The reasoning was flawless; the delicacy and reliability of the apparatus were beyond question. Yet the light did not respond as anything else on earth would have had to respond. Its speed remained the same at all angles, and would not reveal the direction of the earth’s movement.
Later experiments of a far more elaborate kind only proved that the first one had been correct. No observer has ever been able to show any variation in the speed of light. Here is a fact of a different sort from anything else ever investigated by the human mind. It seemed at first a rather slight fact — remarkable, of course, and probably significant, but with nothing revolutionary about it.
As soon as it was established, the mathematicians began to reckon with it. ‘If,’ they said in effect, with all their symbols, ‘this is the fact about light, how must our explanations of other facts be adjusted to it?’ For science has never found two facts in conflict; the mind cannot conceive that two facts could be in conflict. Science is a process of discovering how facts fit together. When science learned how light behaves, it inquired, ‘ What must be the nature of the space and time in which such behavior is possible?’ The result of fitting the new fact to the old ones was some breath-taking conclusions about space and time. The mathematics led far beyond our senses. But at one point after another the astronomers were able, most ingeniously, to check up the speculations by actual measurements of what their eyes could see. The Theory of Relativity was born, and grew, and increasingly persuaded the physicists, helped them forward, never failed them — until now it is the master conception of recent science.
It was not, in its origin, and has never become, philosophical. It made its triumphant way against the most skeptical opposition, because it was everywhere shown to correspond to common sense. It has given a hint of what lies beyond the senses, a little glimpse into the nature of time and space. Huxley would find it fitting perfectly into his definition of science. It has in it no tincture of the mystical.
Another part of recent science has the appearance of being sheer mysticism — the field where men explore the insides of atoms. The space within an atom is so inconceivably minute that it is beyond the senses, beyond even the utmost stretch of imagination. Atoms are so small that a million of them placed side by side in a row would reach no farther than the thickness of the sheet of paper on which these words are printed. Yet rigorously careful scientists have contrived ways of putting out their mathematical tentacles into the infinite smallness of an atom, have measured the forces that sweep about there with inconceivable velocities, and have reported details of this sub-microscopic universe. After twenty years of painstaking exploration, they have unanimously agreed that they have been in contact with definite, measurable realities. They have given the world various hairraising descriptions of the components of atoms.
The pioneer work was done by Max Planck at the beginning of this century. His genius was so deep that Einstein considers him the wisest and most fertile of modern physicists. His great achievement has been the Quantum Theory. In 1927 the brilliant Heisenberg extended this theory to a description of conditions inside an atom. Before we hear it we had best recall what ‘the inside of an atom’ is like.
An atom, despite its inconceivable smallness, is a stable, lawful unit of matter. No one has ever intimated that it has any mystical qualities. Just what is inside of it nobody knows. In 1926 the general conception was that an atom is composed of definite particles of electricity whose size is extremely small compared with the diameter of the atom; by 1927 the fashion had changed, and the internals of the atom were conceived as a system of waves. But the older fashion is still respectable and will not be misleading. The particles are called electrons. They are estimated to be a hundred thousand times smaller than the atom. So the atom is mostly composed of empty space, in which electrons whirl with a rapidity that is too dizzying to name here. It would distract us from our proper business. What we have to fix our minds on is the fact that the study of electrons is a system of mathematics which deals with uncomprehended motions of electric particles that are extremely small compared with the infinitesimal dimensions of the atom.
How the Heisenbergs and Schrödingers secure their data for the exploration of electrons has never been explained to ordinary human beings, but we may feel assured that there is no nonsense about their work. The reason for assurance is that every scientist is eager to expose, pitilessly, the errors of any other scientist. So long as they agree that they are actually dealing in a common-sense way with actual formulas that can be verified, we can trust them. They are in complete agreement — at least for the present — about the actuality of electrons.
In 1927, Heisenberg announced, as a scientific principle, what every physicist accepts as indisputable, what is said on high authority ‘to rank in importance with the principle of relativity ’ — namely: Both the position and the velocity of an electron cannot be determined; the more accurately its position is determined, the less accurately its velocity can be determined, and vice versa.
The ingenious and delightful Eddington at once seized upon this principle, and from it deduced a mystical conclusion: Since the motions are ‘indeterminate,’ they are not caused as motions are caused in large bodies; therefore an electron may act spontaneously; and therefore ‘physics is no longer pledged to a scheme of deterministic law.’ Human will may be free from mechanism.
If this conclusion had been proposed to Huxley as soon as he returned to life, he would probably not have survived the shock, but would have had to quit breathing our twentieth-century scientific air. For the very foundation of science in Huxley’s day was this law of cause and effect. In the very year when Michelson made his experiment, Huxley wrote: ‘All physical science starts from certain postulates. One of these is the law that nothing happens without a cause.’ Yet only forty years later it had become good form to declare that everything inside the atom happens without a cause.
If this statement had been confined to atoms, the world would never have felt much excitement about it. ‘Who cares whether the parts of an atom are lawless?’ we should have said. ‘The poor particles have n’t any real liberty, at that; for they are closely confined within a diameter of one sixty-threemillionth of an inch. Let the little things have their freedom.’ There would have been no human interest in the anarchy that was limited to such infinitesimal dimensions. But Eddington had discovered within the bounds of the atom a hope for human freedom. He issued — as a scientist reasoning scientifically — an emancipation proclamation for the human will. The philosophers read with glad amazement that their souls were not automatons acting solely by mechanical laws, but were uncontrolled, spontaneous, free! ‘Glory be to science!’ said the philosophers. ‘Blessings be upon Eddington!’ cried the theologians. A flood of sermons and essays conveyed to an eager populace the glad tidings that now the human will was free. Halleluiahs were the order of the day.
No frantic vagary of the mind of man has ever been more entertaining than this one, or has exhibited more clearly what emotional animals we are — what incurably superstitious animals. For six clamorous years we have been shouting the slogan of our new-found freedom: ‘Great is the Indeterminacy of Heisenberg!’ The suddenness with which this theory arose, and the violent change it wrought in the modes of thinking, may be gauged by this one fact: The article on ‘Free Will’ in the latest edition of the Britannica was prepared too early to make use of the atomic gospel; it therefore sounds flat and antiquated, because it lacks all the zest with which this most ancient puzzle is now brought to a picturesque solution.
Eddington’s logic has been echoed with plaudits by all manner of intellectual people. It has been accepted by a few unwary scientists. But it has become stale and disreputable logic in 1933. Bridgman had patiently exploded it in the very year when Eddington preached it. In 1930, J. E. Turner showed that Eddington had merely been confused by two meanings in one word: ‘indeterminate’ may mean ‘ not caused,’ or it may mean ‘we cannot determine.’ In 1931, Bertrand Russell agreed that Eddington had merely been deceived by the first meaning, when he should have seen that the second was the true one. ‘The principle of indeterminacy,’ said Russell, ‘does nothing whatever to show that the course of nature is not determined.’ C. G. Darwin, in The New Conceptions of Matter, delivered a similar verdict: ‘It has been suggested that the new outlook will remove the well-known philosophical conflict between the doctrines of free will and determinism, and it has been welcomed by many for that reason. I would personally offer a most strenuous opposition to any such idea.’ In 1932, Herbert Dingle published a book which scornfully enlarged upon Eddington’s error; the great Planck declared, ‘I have not been able to find the slightest reason which would force us to give up the assumption of a law-governed universe’; and Einstein was quoted in the same book as saying, ‘The idea of a free will in nature is preposterous.’ Before the year was out a philosopher, R. W. Sellars, in his most severely reasoned The Philosophy of Physical Realism, spoke thus of Eddington’s epistemology: ‘I have the impression that physics is already getting its balance in these matters. The uncertainty is in our knowledge and not in the event. . . . There is no need of grasping at electronic spontaneity as at a straw.’ Early in 1933 appeared H. Levy’s Where Is Science Going? — a book which was written to show ‘the vicious features’ of Eddington’s argument from ‘ a fictitious world of isolated electrons.’ And three months later, in The New Background of Science, Jeans concluded his masterly discussion with these words: ‘When we represent objects beyond our senses in space-time, their apparent absence of determinism may be merely the price we pay for trying to force a real world of nature into too cramped a framework.’
So it appears that a few scientists, philosophizing beyond their knowledge, have veered toward mysticism. There is no evidence that real science has ever swerved an inch out of its road of accepting only what can be unanimously verified — and retaining it only so long as it continues to be verified.
‘The road of science’ — what does that mean? It means that a bundle of electrons, calling itself ‘man,’ finds itself in a universe of energy and space and time, and tries to make acquaintance with its surroundings. It can receive impressions from one kind of energy, light; and so it says to itself, ‘I see the universe.’ But it has no understanding of what light is, or what seeing is. And as for space and time, man can receive only the most vague and indirect impressions from them. He tries to feel out these forces with his spectroscope and his mathematics — touches them, and calculates his touchings very ingeniously. But his senses cannot take hold of them directly. He has made some progress, so that now he can measure his length against his surroundings. In one direction he is so many quadrillion times the size of an intricate bundle of force that he has named an electron. In the opposite direction he measures a great aggregate of force that he names a star, and he finds that the star is the same number of quadrillion times larger than himself. This is something. He has reason to be proud of himself.
But he has gone only a fraction — he cannot make any guess at how small a fraction — of the whole way of knowledge that science is striving to cover. On either hand stretches an infinity; one he names ‘small,’ and the other he names ‘large.’ But he has no way of telling whether the large dimension is any greater than the small one; for both alike reach endlessly on and on beyond his power to follow the clues of the symbols that represent them. The more he advances, the greater seems to be the distance that unrolls before him. At present he has no intimation of any boundary to his search. He bumps into an obstruction that shows he must choose another direction, or he suddenly swoops forward a great way through clear space. But the impediment may reveal something; the far flight may land him in perplexity. He cannot find out what he is exploring or whether his road has any end. He can only push ahead, impelled by the curiosity that is instinctive in him.
Always, as he squirms along through the unknown, he imagines what may lie ahead, makes pictures for himself. Sometimes these pictures have been the luckiest aids he can contrive for himself — as when some genius fancied the earth going round the sun, or when Newton sketched a design of gravitation. It is this imagination of man, forever running in advance of the senses, which has shown him how to prospect for knowledge, which is now luring the astronomers onward beyond their calculations to places where more headway may be possible.
If these mental pictures are recognized as mere possibilities, they are harbingers that prepare a way through the mysteries. But more often they have been regarded as true just because they are so lifelike. ‘I see a picture,’ said Lamarck, ‘of a giraffe striving to reach higher and higher for food. By continued exercise the animal increases its power to elongate its neck, and this power is inherited by its children. I see all animals improving themselves in various ways by their efforts to fulfill their desires, and I see these improvements inherited by offspring. Look at the great picture that my mind shows you: organisms continually altering themselves for the better and passing on their acquirements to their descendants. This is the way animals developed into higher forms.’ The mind of Lamarck had seen a vivid picture and then declared that it represented reality. The minds of all men naturally do the same. They see an image take shape; they suppose that the image is a reality.
Science acts differently. It scrutinizes a mental picture with interest, and remarks: ‘This may be like reality. Let’s test it.’ It tested Lamarck’s vision by asking, ‘ Where is some example of the kind of evolution that you describe?’ For a century it sought the example. None was ever found. So evolution was discarded. When Darwin offered another picture, science was far more skeptical, even hostile. But the new form of evolution was gradually found to correspond more and more with all the realities that zoölogists and botanists could discover. It stands until someone can discredit it — not a day longer.
‘Evolution’ is a word. It names a discarded notion; it also names an accepted theory. Within this one term there are two opposite meanings. We simians prefer to argue about the word and not trouble ourselves to sort out the meanings. Thus, we infallibly tend toward mysticism. It is the business of science to elude the tyranny of words, to examine what lies behind the words — to escape from mysticism.
Many of our mental pictures are enshrined in words that contain opposite meanings. One of these is ‘faith.’ ‘I have a faith in the law of cause and effect,’ said Huxley. And a religious man says, ‘I have faith in a personal God.’ Whereupon some logician declares, ‘Religion rests on the same foundation as science; both rest on faith.’ It seldom occurs to us to ask for definitions of the word. If we defined Huxley’s faith, and then defined religious faith, we should see that they have nothing in common. For one is universally verified; the other is agreed upon by only a small fraction of the race.
‘I have an experience of God,’ says Eddington. Straightway the word ‘ experience’ forms a picture in millions of minds, and they seem to see a reality of science in contact with God. Then another astronomer announces, ‘ I have an experience of Betelgeuse’; and, as soon as all other astronomers have examined his evidence and corroborated it, the world accepts as real a picture of a great mass of tenuous vapor 260,000,000 miles in diameter. Each man has used the same word, ‘experience’; our simian brain therefore assumes that the experience of God is the same thing as the experience of a red star; and we conclude that science is just as mystical as a mystical religion. A pair of definitions of the two utterly different uses of the term would reveal that the two experiences have nothing in common.
Thirty years ago, a prominent Yale physicist said to a colleague, ‘There is nothing of which we have so much knowledge as we have of the ether.’ Fifteen years later, the physicists discarded the ether and threw it into the lumber room of bygone hypotheses. This would be a pretty story for a college debater to use if he was arguing that science relies on faith as much as religion does. But there is no parallel between a belief in ether and a religious belief. The two kinds of mental operations are confused only because the same word is used for both. The mind of the physicist who thought he knew so much about ether worked thus: ‘ All the evidence we have indicates that there is a substance pervading all space; all competent students agree about the evidence; not one of them can conceive that the ether does not exist; I shall therefore accept it as a probability until there is some new reason for doubting it; I am ready any day to consider any objection that comes from a reliable source.’ But a man who believes in Hell uses his mind quite differently. He says: ‘Only a fraction of the religious experts, and only a much smaller fraction of university professors, believe in Hell, but their disbelief means nothing to me; I feel assured that the majority is wrong.’
The difference in those two attitudes is the difference between science and any other way of using the mind. No scientist ever ‘believed in’ gravitation as a force of attraction. Every physicist has known that gravitation is a mental picture; he has thought that it probably corresponds with reality; but he has been ready at any hour to throw the picture away as soon as it became doubtful. Most physicists quickly threw it away as soon as they understood Einstein’s theory of 1915.
A respectable scientist does not ‘believe in ’ the theory of probability which teaches that once in so many quintillion times a hot fire will cause a kettle of water to freeze, or that once in so many sextillion times a band of monkeys on a battery of typewriters would produce Washington’s Farewell Address. He agrees that these mathematical conceptions may correspond to some form of reality, but he sees a stronger probability that the mathematicians have confused two different meanings of the word ‘probability.’1
Of course, there is a sense in which science ‘believes.’ It does not deny that there is some objective reality in the universe, or that our brain receives impressions from this reality, or that all motions of molecules are produced by some cause, or that heat always passes from a warmer body to a cooler one. Nor does science deny that the mind may be different from matter, or that a personal God directs the universe. But neither does science affirm these statements. For denying and affirming are warlike actions, suitable only for creatures who are unconscious of their ignorance, who are devoted to private dreams and empty logic. Science is the activity of persons who realize what ineffable mystery is, who are curious to explore it.
- See Bridgman’s address in Science for April 22, 1932. — AUTHOR↩