Popular Science Monthly/Volume 13/July 1878/The Scientific Study of Human Testimony III
OUTLINE of the Reconstructed Principles of Evidence.—Even a qualified admission of the soundness of these views also compels the admission that the reconstruction of the principles of evidence is the crowning need of philosophy.
Such reconstruction will not be made on the base of Pyrrhonism, or the denial of the possibility of knowledge—for knowledge is possible, although it is relative to the human faculties. The revision of human testimony that physiological science now requires, and is qualified to undertake, is radical and revolutionary, but it is not suicidal; it is discriminating, not sweeping; not destructive, but constructive.
The demand is not for the rejection but for the reconstruction of human testimony; and the spirit with which this should be undertaken is not skeptical, but scientific.
This reform of logic, like all revolutions in science, should advance under the guidance of the scientific method. By the scientific method, I mean that method of obtaining and organizing knowledge which consists in defining, so far as is possible to expert human faculties, the boundaries between the possible and the probable, between the known and the unknown.
The scientific method can only be successfully used by those who are endowed with, or by discipline have acquired, what I am accustomed to call the scientific sense, by which phrase I mean the power of seeking truth through the intellect alone, uninfluenced by the emotions. For the tendency of truth, the scientific sense has no hopes and no fears, except so far as it may help to find the truth.
The scientific method is a part of the evolution of culture, of science, and of civilization; to absolute savagery everything is absolutely known; all natural phenomena are pronounced supernatural; with the beginning of knowledge there is a recognition of ignorance, which, in time, gradually subdivides so as to include all phenomena that can be brought to the attention of the human mind in one of these four grand divisions—the possible, the probable, the known, and the unknown. The constant effect and sign of progress in knowledge is the narrowing of the area of the known and the probable, and the extension of the areas of the unknown and the possible.
I. The corner-stone of the reconstructed edifice of the principles of evidence must be the recognition of the necessity of the testimony only of experts in all matters of science, and consequent absolute rejection of all testimony of non-experts, without reference to their number or the unanimity of their testimony.
A few definitions are here needed:
Science is systematized knowledge.
An expert is one who can see all sides of a subject.
A non-expert is one who sees but one or a few sides of a subject that has many sides.
The tests of scientific expertness are—distrust of the senses; the recognition of the relation of induction to deduction; avoidance of all sources of error, in observation, experiment, or reasoning; the appreciation of the relative importance and non-importance of real or supposed facts; the ability to distinguish reality and its semblance, especially between the subjective and the objective; and, what indeed follows from the other three tests, the maintenance of mental equilibrium during experimental researches. The reputation of an expert is acquired primarily through other experts, and secondarily through the judgment of mankind. Expertness has its various degrees; there are experts, and experts, and experts: the highest experts are the originators, the explorers, the pioneers, the founders, the creators of science; the lowest experts are the followers, the gleaners, the treasurers, the curators of what others have discovered, and who simply repeat and retain the experiments of genius. The highest experts—the Newtons and Galileos, the Harveys and Jenners of science—must stand at first alone, with no other expert at hand, by which to estimate their relative heights and strength; it is their necessity and their glory to educate experts, by whom their own merits are to be tested; they must create the standard by which they are to be judged; their critics will be their own offspring. For many years Newton was the only man on this planet who understood the theory of gravitation, or was able to criticise it.
The tests of scientific non-expertness are, blind repose in the senses, the inability to eliminate or appreciate sources of error in observation, experiment, or reasoning; the non-appreciation of the relative importance of real or supposed facts; the confounding of semblance with reality, and particularly the subjective with the objective; liability to be entranced, or to have the emotions unduly excited, in the presence of genuine or supposed phenomena; and the use of induction when only deduction is valid, and vice versa.
Expertness in one branch of science not only does not qualify, but in various ways may disqualify, one to be an expert in another branch.
That skill in mathematics unfits one for the successful study of various other specialties was pointed out long ago, both by Abercrombie and Hamilton; but the antagonism of specialties may be traced, under recent experience, yet more minutely, for it is found that eminence in physics, or chemistry, or astronomy, may thoroughly unfit one for the study of physiology; and within a few years some of the greatest blunders recorded in the history of delusions have been made by naturalists, chemists, physicists, jurists, and astronomers of unquestioned honesty, real genius, and deserved eminence, making, or attempting to make, discoveries in the new and almost unexplored realm of cerebro-physiology—experiments with living human beings. The worst blunders in the world are scientific blunders—the unconscious slips of justly eminent men, who do not know that their very eminence in one sphere forbids them to undertake another.
Coöperation of Experts.—There are claims that can only be settled by a coöperation of experts, in different branches of science. In regard to the question of the relations of experts to each other in the investigations of claims, it is to be observed that a claim should primarily be referred to that specialty that is best capable of dealing with it by deductive reasoning. Claims that can be settled by the principles of logic, without the aid of special scientific knowledge—such as, from the limitations of the human faculties, can never be proved or disproved—are to be referred to logicians. If the known principles of any special science, to which a claim is referred, deductively disprove any claim, it is unscientific for any expert in that science to examine or discuss it, save as an amusement, or for the sake of the incidental facts that an investigation may develop. If the claim refer to an open question, the primary expert is to judge whether the coöperation of experts in other branches of science is needed. If the claim belong to a department not yet organized into science—the territorial or preëxploratory stage—in which there are no experts, there are none to decide upon its merits, and the world must remain in ignorance until the experts appear; but the world, in its impatience and ignorance of logic, practically refers such claims to leaders in various branches of science, or to men of general ability and honesty, who almost always reach erroneous, if not ludicrous, conclusions. Such was the origin of the delusions of "animal magnetism," and "odic" and "psychic" force—claims that belong to cerebro-physiology, a department of science that is now but just passing out of the territorial into the organized stage. When experts blunder, as they may, their conclusions should be revised, not by the people, but by other and better experts.
II. The reconstructed principles of evidence require that the quality and quantity of evidence necessary for proof of any claim depends on the nature of the claim.
The principles of evidence that have heretofore commanded the world's acceptance make no distinction in the quality or quantity of testimony for different varieties of claims; the discovery of a new planet is as credible as the daily rising of the sun; the introduction of a new force needs no more and no better auspices than the observation of the established phenomena of an old one; the passing from death into life is to be received with as little question as the passing from life into death. Under this feature of current logic delusionists of all kinds have consistently and persistently found refuge.
The different classes of claims in regard to real or alleged phenomena, in their relation to the quality and quantity of evidence needed to prove them, may be thus presented in order of climax:
1. Claims as to unsystematized knowledge or matters of every-day life.
Under this head comes most of the testimony commonly given in courts of justice. For claims of this kind experts are not usually required, and the mistakes which are constantly made, every hour and every moment, are of comparatively trifling account, since they affect individuals and not general principles.
It is one of the innumerable proofs of the limitations of the human brain, that the rules of evidence in our courts of justice, although practically, on the average, as good, with some exceptions, as can be expected for the obtaining of legal justice, necessarily imperfect and uncertain, are yet, in many respects, to the last degree unscientific. The exclusion, for example, of hearsay testimony, and of the testimony of a wife against her husband, and the modes of questioning and cross-questioning of witnesses make it oftentimes impossible to obtain justice. The scientific man, desirous not of gaining a point but of ascertaining the truth, and recognizing the untrustworthiness or uncertainty of nearly all human testimony, would in many cases prefer hearsay to direct statements, and would give more for the evidence of a near relation or a wife than for that of all the world besides.
One needs but to follow the details of a few great causes, as the McFarland trial, the Beecher-Tilton, the Tichborne, and the Vanderbilt cases, to see that by the rules of evidence, or at least by the actual practice of courts, testimony which scientifically is valueless is admitted, while the only testimony that is, or promises to be, of any scientific value is systematically excluded.
The great advances in science have not been made in courts of justice. Even when on questions of science experts are called to testify, their testimony is obtained in such a way as to impair, if not destroy, its value, and to obscure more than to reveal the truth.
From the scientific point of view, a legal trial is really an experiment with living human beings, and, like all experiments of that kind, is liable to six sources of error, all of which must be guarded against if we are to find the exact truth. The science and art of experimenting with living human beings are not yet understood, even by physiology and pathology, to which department they belong.
2. Claims as to general or special facts of science that are already established by the investigations of experts.
Here we rise in the scale of evidence, but do not require experts. What is bad or useless evidence for original demonstration may be satisfactory, or at least tolerable, for confirmation. The phonograph, prior to its invention, was credible only on expert authority; stories relating to it may now be received on the statements of non-experts, for, although they may be erroneous, they do not in any way affect science.
III. Claims as to facts or phenomena which have not yet been established by experts in the special science to which they are to be referred, but which may yet be proved true by the experts of the future.
Here we take a long step in the ascending scale of evidence; we come to claims that cannot be proved by any amount of non-expert evidence; which may be true, or may be untrue, as experts only shall determine. A type of this class of claims is that of the sea-serpent, of whose existence there is now no proof, but which zoölogists might possibly introduce into science. Testimony which is sufficient to arouse the attention of experts, and induce them to investigate claims that are made by non-experts, may yet of itself have no value in science.
Types of this class of claims are supposed new forces in Nature, the existence of which can only be established by the highest experts in the branches of science to which they respectively belong. The claims of "odic" force and "psychic" force, and of "animal magnetism," are excellent illustrations: although believed by thousands and thousands of people of average intelligence, and by a number of eminent non-experts in science, they are yet instinctively rejected, not because there is any positive deduction against them, but for the reason that experts have never been able to find a shadow of proof of their existence, but, on the contrary, have been easily and abundantly able to show that all the real phenomena supposed to indicate the presence of these unknown forces can be explained by the laws of forces already known. An illustration, belonging in part to a different branch of science, was that of the alleged new force, between light and heat on the one hand, and magnetism and electricity on the other, said to have been discovered
two or three years since by Mr. Edison, the renowned inventor of the phonograph. This claim belonged primarily to physics, and secondarily to physiology, and was carefully investigated by many physicists and some physiologists of this country and Europe, and by them it was decided, rightly or wrongly, that the claim was not proved, that the spark supposed to indicate a new force represented a hitherto undetected phase of induced electricity.
IV. Claims which, from the limitations of the human faculties, can never be proved or disproved.
Claims of this kind may be indulged in as speculations, with the understanding that they are merely speculations; but to seriously discuss them, with the purpose of ascertaining their truth or falsity, is unscientific.
Under this head all supernatural claims must be included, for the reason that it is impossible for the human faculties to distinguish between what is unknown in Nature and what is above Nature. The narrow limitations of our knowledge of Nature all will admit. What expert professes to exhaustively know Nature even in his own department? What, indeed, is all our knowledge but an infinitesimal fraction of our ignorance; a flower or so plucked from a boundless garden; a few ores dug from measureless mines; a slight clearing in an infinite wilderness; "a film on the ocean of the unknown?" Leaving out of view all questions of supernaturalism and all the phenomena of life, what do we know, or, in this world, have we reason to expect to know, of inorganic Nature? What is light? What is heat? What is gravity? Why should one mode of motion make one form of force and not another? Toward the solution of these primal questions—that the infant can ask and the philosopher cannot answer—the sciences and reasoning of all the centuries have made, and are destined to make, no advance.
Even if an expert could be supposed who should exhaustively know Nature in his own department, how could he know that he knew it? Not knowing that he knew all Nature in his own realm, what tests would he have—could he have—to distinguish between the supernatural and what might be unknown in Nature? If, to go to the outermost verge of conceivability for illustration, the clock of the universe were turned back to-morrow, and the sun should thereafter rise in the west instead of the east, how would it be possible to prove, in a scientific sense, that a supernatural event had occurred?
Every phenomenon that can be brought to the attention of the human faculties must be referred to one of these three classes:
1. The known in Nature.
2. The unknown in Nature.
3. The supernatural, or above Nature.
In investigating any new claims whatever, experts—consciously or unconsciously—keep this order in mind: they first inquire whether the claims can be explained by laws already known to experts; if not so explained, then they are referred to the second order—the unknown in Nature—and attempts are made to bring them into the first order, or the known in Nature: such is the philosophy of all human progress in science. But when men go further, and assert that these unknown phenomena are of supernatural character, they bid good-by to the scientific method; for what is it that constitutes the differential diagnosis between the unknown in Nature and the supernatural? It matters not, in its bearings on this question, how the supernatural is defined, as the unusual action of natural laws or interference with natural law. The supernatural manifested becomes, relatively to the human faculties, the natural. For all that we know, or can know, every great or minute phenomenon in Nature may be a direct, immediate, and special act of a power above Nature: the movement of every star, each vibration of the infinite ether, the shock of earthquakes, and the silent meaning of protoplasm, may all be manifestations of a power above Nature; but, whether they are so or not, the human mind is powerless to prove or disprove. The universe might swarm with demons and angels; ghosts might inhabit the earth and sky, in numbers compared with which the population of the globe is as the seen to the unseen stars; spirits might speak, might rap, might materialize—and yet the human mind would be unable to scientifically prove the supernatural, for still the question, how to distinguish what is above Nature from what is unknown in Nature, would remain unanswered and unanswerable.
Science has not, cannot have, any absolute deduction against the existence of ghosts, or of spirits, evil or good, or of any imaginable supernatural shapes whatsoever; the world might be embraced and permeated by an infinite spiritual ocean, as the air is believed to be penetrated by a luminiferous ether; but science would not have, and could not find, either through induction or deduction, any way of demonstrating its existence. In the realm of the supposed supernatural all things are possible and all things are undemonstrable. Under this class of claims, that from the limitations of the human brain can neither be proved nor disproved, are the conventional definitions of matter, and accepted distinctions between matter and mind, or other forms of force.
The qualities that for ages have been attributed to matter, as inertia and extension, apply correctly enough to that limited portion and form of matter that the senses can appreciate; but, as has been shown, all but an infinitesimal portion of Nature is permanently sealed against the senses. What warrant have we, beyond undemonstrable probability, that the attributes of that portion of matter that can be reached by the senses belong also to all that portion of which the senses can directly teach us nothing? How do we know that the familiar forces, as light, heat, electricity, and gravity, may not be as truly matter as the Atlantic Ocean or Mont Blanc?
Standing on the outermost verge of conceivable science, and casting the line of probability into the dark unknown, as far as it is possible for human weakness, will it, can it reach any more rational generalization than this, that all Nature is unity? Whether the common axioms of human reasoning—such as the whole is greater than a part, every effect must have an adequate cause, every thought must have a thinker, a thing cannot be and not be at the same time—do or do not apply to the supernatural, the mind of man is powerless to determine.
Under this head come all conceivable questions relating to the existence and nature of other universes than ours.
A question of great interest, or would be if it could be answered, is that of spontaneous generation, which from the limitations of the human senses can neither be proved nor disproved.
How is it possible for the human faculties to determine what degree of heat any supposable living substance, or intermediate substance between living and non-living, beyond the reach of the microscope, may bear? There are gradations of endurance in living things that are accessible to the senses. What are the limits of this gradation through the realm of the infinitely little? If, therefore, all experts in this branch of inquiry should agree that fluids subjected to a very much higher degree of heat than has yet been employed in experiments of this kind shall yet, when every conceivable precaution against sources of error has been taken, develop some of the lower forms of life, the question of spontaneous generation would still be an open one.
The present and prospective state of the spontaneous generation question is, then, as follows:
1. Science has no absolute deduction for or against it.
2. It is impossible by present deduction or by conceivable induction to either positively prove or disprove it.
Discussions on the subject, like that between Tyndall and Bastian, are on both sides unscientific, as they are unsatisfactory, and would not be indulged in by those who have correct ideas of the limitations of the senses.
V. Claims which are absolutely disproved by deductive reasoning, and which therefore the special sciences to which they belong know to be false without any examination.
Among the more prominent of claims of this kind are those that relate to squaring the circle, flatness of the earth, perpetual motion, including "Keeley" and "Winter" motors, alchemy, astrology, "four dimensions of space," levitation, mind or thought reading, clairvoyance or second-sight, including prevision and retrovision.
To examine or discuss claims of this kind, for the purpose of determining their truth or falsity, is not only useless, but unscientific. In science there are three unpardonable sins—trusting the senses, non-experts attempting to do the work of experts, and using deduction for induction, or, vice versa, induction when only deduction should be used, as in the class of claims here under consideration.
The reconstructed principles of evidence explain the following problems in psychology, to which hitherto, so far as I know, no solution has been offered:
1. Why the logic of the schools has always been on the side of delusions.
For those who accept non-expert testimony science is the only delusion: everything is true except the truth. In the long discussion relating to various modern delusions between Mr. Wallace and Dr. Carpenter, Mr. Wallace, according to the rules of evidence, has throughout the best of the argument: his reasoning, for those who trust their senses, who believe that non-experts can do the work of experts, and who use induction when only deduction should be used, is unanswerable.
Likewise in all, or nearly all, the world's memorable contests between science and delusions, the truth has prevailed, not by virtue of logic, but in spite of it; the instincts of mankind—the one saving clause in the constitution of the human brain—rising up in their unconscious majesty, and vindicating their rights and their power against the tyranny of the senses and the cruelty of the syllogism. Logically, Copernicus and Galileo were wrong; and their accusers, backed by the concurring testimony of the eyes of all mankind through all the generations, have to this hour never been answered. Only on the side of error is there consistency; during all these recent days, when science sets its forces in array against any dominant delusion, as "animal magnetism," or "odic" force, or "psychic" force, or "spiritualism," it first closes its books of logic and forgets all the teachings of the university.
2. Why men of culture and genius, and especially of logical attainments, are more easily and profoundly deceived by delusions than men of ordinary ability.
The history of all delusions, so far as known, establishes the wisdom of the maxim of the father of modern conjurers—the famous Houdin: "It is easier to dupe a clever man than a fool." Jugglers, and illusionists, and sleight-of-hand performers of every grade, prefer examining committees composed of leading citizens—the ablest jurists, physicians, merchants, clergymen, scientists, and men of letters that can be found—and instinctively dread the criticism of children and of day-laborers, who, being unable to read, or write, or to think, or to reason according to the books, are obliged to trust their instincts.
The world's greatest follies and darkest untruths, especially while in the process of dissolution, have always found some justly honored authority in theology, in literature, in philosophy, in law, and in science itself—a Matthew Hale, a Lord Bacon, a Wesley, a Cotton Mather, an Elliotson, a Hare, a Gregory, a Wallace, an Emerson, an Agassiz, a Zollner, committees of learned academies, professors in great colleges—to stand by their bedside, armed with syllogisms, trusting their senses, and conscientiously striving to nurse them back to vigorous life. This grotesque phenomenon of history—so universal as to command general observation—would seem to have this threefold explanation: 1. The fact here suggested, that clever natures trained in logic are obliged to reason logically, and, as the logic of the world is wrong, they arrive at the wrong conclusions, which, against the protestation of their instincts, they are forced to accept. The greater the man the greater his errors; the weakness of the world confounds its strength; ignorance is saved by its instincts, which science and logic dare not always trust. If the chart be wrong, the navigator who accurately steers by it is sure to go out of his course; while he who goes by blind reckoning may possibly float into harbor. 2. The social and professional position of men of genius and ability is constantly compelling them to undertake investigations in departments in which they are not authorities, and requires them to proclaim positive decisions which, like the results of all non-expert investigations, are almost inevitably erroneous. 3. The faculty of wonder that so often leads to credulity is not inconsistent with the highest scientific genius; it is, indeed, a powerful and determining element in the scientific character, and thus what has been called "the foundation of all philosophy" also becomes the foundation of all folly. Such, as it would appear, is the solution of the problem which for so many years has been the despair of the historian and the opprobrium of psychology.
Hence it is that there are no superstitions that are so superstitious as the superstitions of scientific men. Hence it is that all delusions in their decline cast their last shadows over the loftiest heights of science, of literature, and philosophy.
- The philosophy of the world has almost always been the servant of delusions. The most eloquent passage in Sir William Hamilton's "Logic" is that in which he enjoins on the philosopher the duty of seeking truth for its own sake, and there are few or no philosophers who would not in the abstract subscribe to this sentiment, but concretely and practically nearly all human reasoning on logic and the principles of evidence has been exercised for the special purpose of proving what is absolutely undemonstrable or absolutely untrue.
- Mr. William Crookes, in his kindly and complimentary remarks on my theory of trance, as republished in the London Quarterly Journal of Science, January, 1878, observes that there may be a physical side to physiological experiments. The suggestion is so far forth a valid one; the reply is found in the above analysis. The question whether there is in the human body a new and unknown force belongs to cerebro-physiology, and, not being disproved deductively, should be referred to those experts in that specialty who understand how to experiment with living human beings; and it is for these primary experts to decide whether the experiments they may make require the coöperation of physics, or chemistry, or other branches of science. There may also be a physiological or pathological side to physical experiments; thus the "etheric force" of Mr. T. A. Edison was primarily a question of physics, but for its investigation needed and obtained the coöperation of physiologists.
- That the art of experimenting with living human beings is now but in its early childhood is shown by the fact that all those who give special attention to the physiology and pathology of the nervous system do not, in their experiments, even suspect the elements of error involved. During the past year one of the very ablest of neurologists—Charcot, of Paris—has published accounts of experiments in so-called "metalloscopy" and "metallotherapy," in the making of which, according to his own statements, one of the most important of the six elements of error (as indicated in a paper on "Mindreading," in a previous number of this Monthly), mind acting on body, seems to have been ignored or ill understood, or at least not scientifically provided for. The experiments of the committees of the French Academy with "animal magnetism," "mesmerism," and "clairvoyance," of Crookes with Home, of Wallace and Zollner with Slade, are open to the same and also numerous other criticisms. From such accounts of such experiments, even an expert cannot tell what did or what did not happen; it is therefore unscientific to discuss them.
- Mr. Edison's views, as he writes me, are unchanged. His experiments, and my own made in cooperation with him, as well as a discussion of the bearings of the claim on the principles of evidence, were published two years since.
- Although it hardly comes within the scope of the present outline to point out all the practical bearings of this reform in logic, one thought may perhaps be briefly suggested. For the cause of religion, it is fortunate that it cannot be scientifically proved. Religion, being a recognition through the emotions of a spiritual universe and of our relations to it, cannot and should not appeal to the intellect. A religion scientifically proved would be a religion no longer, but a fact of science, like the Copernican theory, or gravitation, and, like these and other scientific facts, would be taken cognizance of by the intellect alone, consequently it would lose entirely the leverage of the emotions, by which it has so powerfully influenced the destinies of mankind. The scientific demonstration of religion would be the destruction of religion.