Popular Science Monthly/Volume 81/July 1912/Is a Scientific Explanation of Life Possible?
|IS A SCIENTIFIC EXPLANATION OF LIFE POSSIBLE?|
UNIVERSITY OF MICHIGAN
THE restoration of this question in recent times to a position of some apparent respectability among the biological problems of the day is a striking example, not only of the vitality of misconceptions, but also of the vanity of men. Of course, we do not know all about life, or anything else, and probably never shall, but the outcome of this confession bears no resemblance whatever to the hopeless figure of a future, discounted, and forever condemned to total silence. To refuse the men of to-morrow the chance to explain what they can, may produce in some minds a pleasing artistic, or even philosophic effect, but no one can cut short the road to truth, or travel thither on his own terms, for the conditions under which nature transports us are rigid, unfavorable, and as plain as the rules printed on a railroad ticket. Nor is the rate low, for she demands not only money and unlimited patience, but all of our fondest prejudices, and our most natural and ingrained faults as well, must be left at the station window, before we depart. Nature gives passage only to modest folk who do not pretend to know everything before they start, and who are ready to give up the past, and let bygones be bygones.
If I were to ask for a scientific explanation of rain, I should be told that at a given temperature and barometric pressure, the air dissolves a limited amount of water vapor which evaporates chiefly from the surface of the ocean, and rises in the sky. When cooled, as it often is at high levels, or by chilling winds, the vapor condenses, and if the cooling proceeds beyond a certain point, the minute spherules that make up the cloud, enlarge by fusion to droplets that fall. Some of the drops that leave the cloud are larger than others, and in falling overtake the smaller ones, as the giant drops gliding down a window-pane devour the pigmies in their path.
While the answer given is incomplete, it is nevertheless useful, and should serve my purposes, for by means of it I may decide whether or not to go on a picnic, or to plant a crop. Of course I might ask for more information on evaporation, and for further details concerning the condensation of evaporated substances and whether the end-products of these two processes are identical. I might also wish to know more about the fact that sometimes a substance rises from the ground and sometimes it falls, and furthermore, how it happens that in a vacuum small drops and large fall at the same rate, but, however many questions I might ask, from the man of science I should receive answers which, though differing in richness of detail, in principal would be invariable.
What is this principle? No matter how much the physicist, the chemist and the meteorologist might add to the chain of events as outlined, it would never be other than a chain of events. Even at the present time it might be lengthened almost indefinitely, and although this might show how much we know, it would also show no less clearly that all our knowledge is of one sort, and that scientific explanations, however many or few links we may have in our chains, never amount to more than the enumeration of the conditions under which the events in nature take place. Under the proper conditions evaporation occurs; when the conditions are right a cloud is formed; and, under the proper circumstances, rain falls. This is the chain; in it one event is the outcome of certain conditions and on its shoulders stands the next event if other conditions no less important have been satisfied.
There is something very instructive about a series of this kind, for study, not only of the conditions under which rain falls, but of the conditions under which anything whatever happens in nature, shows conclusively that all the conditions are equal in importance. We ourselves are such poor democrats, however, and so accustomed to special privileges, so much more interested in some things than in others, so inured to our worship of the exceptional and the peculiar, that when we meet with a situation like this, the language of the street, the habit of a life-time, and the teaching of centuries all unfit us for the task of interpreting nature as she really is. Nature is democratic; that which is the condition of an event is neither more nor less than that event's condition, and when, as is always the case, a group of conditions is the basis of an event, that event is suspended, or another takes its place, unless the tiniest condition has cast its vote in the primaries.
It is the neglect of this truth that leads to many of the difficulties of science, for her most ardent votaries are often bent on bestowing special favors among conditions, and now and again knight them. But knighthood among conditions is as precarious an honor in science, as a seat in the house of lords, for sooner or later the bogus knight falls in joust, and another, himself soon to be vanquished, takes his place. It has happened many times in the history of science, one need but think of the changes in the treatment of disease that first one cause, then another then a third has been assigned the leading role in the drama of causation, but each of these in turn has had his vizor torn off, and has stood exposed as a condition which, masquerading under the armor of special privilege, for a time succeeded in imposing on the public as a real cause. Indeed, no one who has set out on the quest for causes in science, has ever returned with anything else than a knowledge of conditions, for the fountain of action escapes them as the fountain of youth receded before the searching eyes of Ponce de Leon. Nevertheless, the treasures on the road of the deluded are no less valuable than those strewn on the pathway of the sane, if they will but pick them up, and all the wealth of our much boasted “causal” biology has been brought home by men who were not lucky enough to get what they were after, but wise enough to take what they could find.
Those who have parted with their entire wealth of prejudice in the matter of causation can safely begin to discuss the question whether scientific explanations, explanations by means of chains of events, can be legitimately applied to vital action, and furthermore whether such explanations are useful. At the outset, however, they meet with a grave difficulty, for at the present time no one knows exactly what it is that needs to be explained. Some tell us, life is motion; others call it a chemical-physical process; whereas some declare it synonymous with consciousness. Herbert Spencer, after cudgeling his brains for many years, arrived at a statement which seemed to him, as it has to many since then, the best possible. “Life,” he says, “is the continuous adjustment between internal relations and external relations.”
Unfortunately none of these definitions is really satisfactory. Who, on being told that life is the continuous adjustment between internal and external relations, can feel that now he has the secret firmly in his grasp? Indeed at present a hard and fast definition is scarcely possible, and, if it were, would add more to the comfort of the dialectician than to the progress of knowledge. When we understand life the definition will come of itself, and then no one will care to use it.
Most of the biological work of to-day is an attempt to find out exactly how living things make their living, and the biologist, regardless of his party affiliations, is happy to say that all who study these questions agree that living things make use of machinery. Is not the respiratory system a machine by which oxygen is taken from the air and carbon dioxid given off to it? Is not the digestive system a factory which changes food-materials into simpler compounds that are absorbed?
The machinery of living things is very remarkable, complex, and adequate. It may not always be wholly adequate, but certainly in general it is sufficiently so. Sometimes it can be improved by surgery, by the prescription of glasses, hearing trumpets, false-teeth and tonics, but on the whole it is adequate, it is fit. Indeed, fitness more or less pronounced, but fitness, nevertheless, is the leading characteristic of living machinery and its processes, and under shifting external conditions, distinguishes them clearly from things not alive. No man need take the time to adjust himself consciously when he deals with his fellowmen, with horses, dogs and with building materials. Our familiarity with the striking peculiarities of these substances is such that we pass with the greatest readiness from one to the other, and treat them all in essentially suitable ways.
What do we know about things that are fit in an ever-changing environment? In the first place they are things which have had a long history, and though we are stillignorant of the conditions under which this history has been worked out, we do feel reasonably certain that all life is of a common stock, and that we have as good reasons for speaking of the brotherhood of living things as we have for speaking of the brotherhood of men. We know with much greater detail that fit things assimilate food, that they excrete wastes and that they secrete substances useful to themselves. We know too that they grow, repair wounds, and often restore very complex lost parts; that by a marvelous process of development they reproduce their kind from spores, gemmules, buds and eggs; and finally, we suspect that many of them have minds in some way like our own. We know with certainty that we ourselves have sensations, feelings, emotions, knowledge and the power to communicate much of all this to others. Strangest of all, we have a fairly complete equipment of self-knowledge, and we spend much of our time in thinking and talking about our origin and our destiny.
The anatomist tells us that things which do all this are composed of many complicated parts visible to the naked eye; the histologist analyzes these parts or tissues microscopically, and finds that they are made up of unit masses, the cells, or of the products of cells. From the embryologist we learn in detail how each of the myriad cells of the body comes from preexisting ones, and how by tracing development back to its earliest stages, we finally reach the egg. Cytology carries the dismemberment a step farther by discovering, classifying and naming, not only the minuter parts of the cell, but its very granules. Biological chemistry tells us what substances are found in the protoplasm; chemistry what elements are present and their proportion; physics that these elements are molecular in structure, that each molecule is made up of smaller units, the atoms, and finally, the newest physics of all dissects the atoms and promises to show that these, instead of being simple, are in reality constellations of electrons. When we consider that a single protein molecule may contain perhaps 2,304 atoms, more or less, that the number of protein molecules in a cell is unknown, that there are millions of cells to the man, we realize that our bodies are fearfully and wonderfully made, and that if our ears were sensitized to only a fraction of the rush and bustle within each protein molecule we should be deafened as with the roar of a Bessemer furnace.
This analysis is far from complete, but thousands of men throughout the world are contributing, each the small share which he can, toward the unraveling of the great puzzle. Those who know most are least hopeful that we shall ever know all, but many will subscribe to the statement that the resolution into electrons is the last station suspected at the present time on the road which we are travelling. It is an interesting question, therefore, to consider what we shall have accomplished when we have resolved man by analytical methods until we can name each one of the electrons of which this remarkable being may possibly be composed.
In the distant future some Super-Zeiss may possibly make a lens more powerful and strange than Aladdin's lamp. In its focus, a man, with electrons as large as coffee-beans, would be but the transparent ghost of his real self, and the rush and swirl of his elephantine heart and the monstrous hailstorms rushing in and out of the elastic cloud-like lungs would startle and confuse even the hardened physiologist of those days. Under the circumstances the self-control constantly employed by every good observer might easily leave him and his cries of astonishment would probably be answered by cataclysmic tossings among huge masses of the illuminated brain of the man who was told to keep still and pay no attention to the professor.
The knowledge implied in all this transcends the whole of human experience, but there is no man of science worthy the name, who would not welcome it, or who does not hope that some day we shall understand these things better than now. If we throw ourselves into the future when the sort of knowledge to be got with the Super-Zeiss Illuminating Magnifier shall have become common property, we can imagine even the men on the street possessed, not only of astronomical acquaintance with living bodies, but also with the world in which these bodies live. These super-men may know that certain changes in the movement of the surrounding electrons are invariably followed by certain movements of the electrons in the brains and hearts of their fellow-men; they may know exactly what torrents and back-eddies of corpuscles occur when two friends who have not seen one another in twenty years meet on the pavement, and they may be able to describe in much detail the wild turmoil in the nervous system of the lunatic. But they will not be able to see the joy which friends experience on meeting nor the delusions of the insane. We may confidently expect them to have their own joys, sorrows, and imaginings, and that they may know what the physical concomitants of pleasure and pain in others are, but no feeling or thought will be theirs except their own. In this respect they shall be no wiser than we are, for we too can tell pleasure and pain when we meet them, but whereas we recognize them by smiles, laughter, lined faces and tears, the men of to-morrow may know these things by the movements among electrons.
Although physical analysis of men can never give us more than the physical symbols of their consciousness, it would be the height of folly to consider this information complete, for it leaves out the most important thing about men. This greatest asset of all so transcends in value to us the knowledge of its physical basis, that even if every feeling and thought we have comes only with such changes in our brains as a skilful chemist and physicist might detect, measure and tabulate, it still remains true that we have used and are using our minds advantageously in the almost complete absence of such records. Had Shakespeare been dependent on a knowledge of the chemical changes in his nervous tissues as he wrote Hamlet, it is needless to insist that the play would not yet be written. To know a thing, to perceive and appreciate beauty, to recognize natural law and truth, all these are experiences in consciousness whose value and importance in human life no man can deny, nor can any man give a satisfactory explanation of the actions of his fellow-men without considering their feelings, emotions, and thoughts.
Since consciousness must be reckoned with in a scientific explanation of men, the question arises whether something analogous is not also true of living things in general. Does not the fitness of living things, the fact that they perform acts useful to themselves in an environment which is constantly shifting, and often very harsh; the fact that in general everything during development, during digestion, during any one of the complicated chains of processes which we find happens at the right time, in the right place, and to the proper extent, does not all this force us to believe that there is involved something more than mere chemistry and physics? Does not all this show that there must be present something, not consciousness necessarily, but yet its analogue—a vital X?
If we begin with what each one knows best of all, we may say that we can not doubt the existence of consciousness in ourselves. By intimate association with our fellow-men, and by comparing their acts with our own, we infer that they too are conscious, though we do not know this with the same certainty with which we know it of ourselves. If we descend in the scale of life, we know that it is practical to deal with many animals as though we knew for certain what in all probability is true, namely, that they also are conscious, but when we descend still farther, and reach forms built on a different plan, forms devoid of sense organs, and of brains, forms leading totally different lives, and with responses often simple and direct, what shall we say of them? Are they conscious? Is the amœba, the germinal disc of a hen's egg, or the sapling oak conscious? Nothing short of a method of communication as complete, delicate and trustworthy as the language of men, could ever enlighten us on this question, unless indeed we could transform ourselves at will into amœbæ, hen's eggs or oak trees. Even then we might not know, for we might lose the organ of conscious memory on the way down to the beginning of things, a path up which, in a very real sense, every human being has come in person.
If the question whether living things are conscious can be answered positively in only one case, and with great probability for the rest of our fellow-men and some few of the higher animals, but not at all for the lower forms or the early stages in the development of the higher, practical needs force us to act on our ignorance, and to deal with these matters as they appear to be and not as they might be, although we cannot dogmatize and must grant the reasonableness of William Keith Brooks when he says: “As for myself, I try to treat all living things, plants as well as animals, as if they may have some small part of a sensitive life like my own, although I know nothing about the presence or absence of sense in most living things; and am no more prepared to make a negative than a positive statement.” I do not know whom we should consider the greater fool, the man who went abroad declaiming about the unconsciousness of the oak, or him whom we should discover trying to teach an oak the Greek alphabet.
This is where we stand on the question of consciousness, but the question of the vital X is even more difficult, for we have no experience of it comparable to our first-hand knowledge of consciousness. I have not the faintest idea what living is like except as I know this consciously, for unconscious knowledge or experience is altogether outside my line of business. Hence if there is a vital X in ourselves other than consciousness, I know nothing about it, and if I can not even be sure of consciousness in most living things, I certainly can have no good reason for assigning to them an X of which I not only know nothing, but have no present means of knowledge.
The progress which scientific explanation has made in our own lives, however, should warn us that no one can tell what will come next. It is by no means inconceivable that some day we shall be so familiar with the physical-chemical changes which to-day we know as feelings and thoughts, that we shall be able to infer consciousness from these reactions with the same certainty with which we infer now that a match lit under the nose of a fellow-man has hurt him in much the same way as it would have hurt us.
To my way of looking at things, there are only two possibilities with respect to the vital X, and when the day comes on which the inference of consciousness from its physical symbols shall seem safe and just to the man of science, these possibilities will stand out even more sharply than they do in the present scientific dawn, for the man of the future, equipped with the knowledge with which we have endowed him, will be able to decide whether the X in question is a variety of extra-personal consciousness or a variety of nonsense.
So far as the second of these possibilities is concerned, the men of the future will be no better fitted to deal with it than we are, and as for the first it is practically like the other, and useless as an explanation for an explanation which by the nature of the case we can not understand, is a contradiction in terms.
Aside from the impotence of the vital X as an explanation, its spokesmen are guilty of reasoning unbecoming to men of science, for they attempt to furnish us with an efficient cause of vital action, a captain who steers the ship of life. But consciousness, the nearest known possible relative of the problematic X, is certainly not a cause in man's life, for however much prejudice may incline us to adhere to the opposite view, consciousness is neither more nor less than a condition. It is true that we must recognize it and deal frankly with it, for in its absence man's life assuredly would not be what it is. But the same thing might be said of respiration, of digestion, of the environment, or of any one of the multitude of conditions under which life occurs, and is what it is. And the same thing would unquestionably be true of the vital X, for if it could be proved to be something with which he who would give a scientific explanation of life must reckon, if indeed it were shown to be the element without which it is impossible to understand how the right thing happens in the right place, at the right time and to the proper degree, science instead of having engulfed a real cause, would simply be enriched by the capture of one more of the conditions under which some of the substances in nature live.
If nature were a limited system, there would be some hope of ultimate acquaintance with all the conditions of life, but as the universe is unlimited, no foundation for this hope exists, and one need but reflect, as Brooks did, on the growth of knowledge to realize the truth of these words:
We are told that “when every fact, every past or present phenomenon of the universe, every phase of present and past life therein, has been examined, classified and coordinated with the rest, then the mission of science will be complete.” But if we are to judge the future by the past, classification and coordination will always show us more unclassified and uncoordinated things than they classify and coordinate.Each new encyclopedia is bigger than the one before, and so, no doubt, it will be to the end. If knowledge were nothing more than comprehension, or the analysis and classification of facts, the progress of science should be bringing us nearer to universal knowledge, but each new discovery puts it farther from our grasp than before, and they who know most, are most convinced of its unattainableness, not because the reality of things is unknowable, but because of the innumerable multitude of things knowable.
But even if nature were a limited system and we were able to get into possession of all the conditions under which any event within this system occurs, we should still be no better off, for the external conditions under which our imaginary system would be what it is, could never be known. The student of life, of chemistry, of physics land all others, would find their experience hedged in by an impenetrable wall, beyond which they could not go. In an unlimited world, however, there can be no theoretical limit to experience, and while at any time we are actually hedged in by our ignorance, this wall is fortunately capable of being moved by human powers, and the road to further exploration is clear for all who wish to go that way.
Since exhaustive knowledge in an unlimited universe is clearly unattainable by us, it follows that a scientific explanation is a growing explanation, and of necessity always incomplete. So far as it goes, we have a scientific explanation of life to-day, but it satisfies almost no one because the most important things remain unknown, and our explanations are inadequate to meet our practical let alone theoretical needs. These inadequacies have tempted many to fill out with art what they lack in knowledge, but the deficiencies of science, coupled with the certainty that there is no limit in a limitless universe, to what we may find out, to the man who is true to the scientific standard, are the greatest stimuli, for there is no joy equal to that which comes from extending the bounds of knowledge, for even though she tells us nought of "lunar politics," nevertheless, “all the things thou canst desire are not to be compared unto her.”
To many men the realization that the work of science is unending and that she can extend no hope of ultimate explanations, comes as a blow, but this is neither more nor less than the just reward of all who take the universe lightly. This particular limitation biological science shares with all her sisters, for her failure to give us anything else than the physical symbols of life is a shortcoming by no means peculiar to the application of scientific explanations to vital phenomena. The physicist might analyze hydrogen and oxygen with the same magical lens which we applied in imagination to man, and if present opinions are correct, he would see the constellation of electrons that constitute the hydrogen atom and the constellation that makes up the oxygen atom. If he were an experimental physicist, he might take an electron out of the hydrogen atom and replace it by one taken from the oxygen, and be surprised, or not, according to his preconceptions, that substitution makes no difference. Further analysis might tell him that the hydrogen constellation differs in the number and movement of its constituent electrons from the oxygen constellation, and that both constellations are differently related to the rest of the world, but why one set of relationships should be hydrogen and the other oxygen would be revealed to him as little as it will ever be revealed to the biologist why one kind of corpuscular movement in the brain means pleasure, whereas another means pain.
Unfortunately, the biologist has no more senses than any other man; all that he tries to do is to use those he has to the best of his ability. It so happens that the senses with which he learns, and the brain with which he reflects, have evolved from simpler conditions, but however different the early stages of these organs may have been, they were elements in the fitness of his progenitors, and he believes that his natural endowments, limited though they be, are no less serviceable to himself and his fellows now than they were in pre-historic days. Today more than at any previous time in the history of civilization it is coming to be recognized that the results of the application of our senses to the study of nature are racially essential. Another and closely related truth, however, still has to fight hard for its daily bread, for it is unfortunately by no means generally known that scientific results are not, and can not be, got directly for the asking. Most men of his day, had they known about it, would have considered James Watt a fool, for instead of watching the steaming mouth of a tea-kettle, a thing which millions of men had seen before, and have seen since, and to no particular advantage either, he might have been occupied with the more obviously useful task of chopping wood for the fire; yet to these fireside dreams we can trace the whole of modern travel by steam. Perhaps Gregor Mendel, in the opinion of those who saw him pottering over his peas, would have done better to devote more time still to the affairs of his extraordinarily well-run abbey, yet upon his careful, thoughtful and beautiful observations rests the modern science of heredity, and the hope for the betterment, not only of our plants and animals, but of our very selves. Perhaps the man who hunts for frog spawn in the early spring would be better occupied removing the ashes from his cellar, yet it was a man with just this vagary whose tadpoles not only enlightened him and all the world as to the manner in which nerve fibers grow, but the methods developed in the course of these studies are now being applied for the purpose of determining the conditions under which cancerous growths occur, and consequently are freighted with the possibility of both the prevention and cure of this terrible scourge of middle and old age.
This is the method by which scientific explanations and their application come about, and however much we may regret that knowledge does not grow more simply and directly, the reason for this lies in the structure of nature herself. Nature is a great system of things wherein mediately or immediately everything is related to everything else, and the scientific problem is the discovery of these relations. That many of them are so remote that no man could have foreseen them, is not our fault.
It is this remoteness of natural relations that so frequently startles us when discovered, and it is likewise the remoteness of things that justifies every stroke of work on problems the solution of which no man can evaluate in gold or silver. Indeed our usual standards break down completely here, for the measure of science is not in money, but in happiness, and the market value of this is uncertain, since no man, consciously or at least voluntarily, places his own happiness on sale. To ask for the monetary equivalent of the scientific discovery that our bodies are derived from a single cell, is like asking for the price of a friend. Brooks, in a suggestive paper on universities, wrote:
If material benefits, however, had been the only products of scientific explanation in his day, Huxley, according to his own confession, would not have been cared greatly to toil in the service of science, but would have enjoyed equally well the less complicated activities connected with quietly chipping his flint ax after the manner of forebears a few thousand years back. He tells us:
It is more important, infinitely more important, that I should know and understand the immediate as well as the remote consequences of any action of mine, than it is that I should travel in seventeen hours, in luxury, to New York, and scientific explanation enables me to do both.
It is because we are apt to be so much more impressed by a practical application than by the conditions under which such application is possible, so much more by prominence than by importance, so much more by the gun than by the man behind it, and lastly because science modestly acknowledges her limitations, that she has fallen into ill repute in many quarters. But Cinderella, to paraphrase Huxley's apt characterization of science, modestly conscious of her ignorance in high matters, lights the fire, sweeps the house and provides the dinner, and in reward for this, is called a base creature, devoted to low and material interests. But this charge shows nothing so well as ignorance of her ways, for in her garret she has visions of the order which pervades the seeming disorder of the world, visions of the great drama of life, with its full share of pity, terror and also of abundant goodness and beauty. She has at her command, knowledge which she is ever ready to place at the service of those who will use it, and she knows enough about ethics to foretell social disorganization from immorality with the same assurance with which she predicts bodily diseases from physical trespasses. No brighter light than hers is set for mortals in all the firmament, and by its light, dim though it be at times, we must walk, devoutly thankful for the few rays of insight that now and again illumine the path.
- Brooks, W. K., “Intellectual Conditions for the Science of Embryology,” Science, Vol. XV., pp. 453-454.