And here I lay out of view entirely the comparative dignity of man as a being whose existence is to be accounted for by the one hypothesis or the other, because this comparative dignity is not properly an element in the question of probability. The doctrine of evolution, as expounded by Darwin and other modern scientists, may be true, and we shall still have reason to exclaim with Hamlet, "What a piece of work is man!"
On the other hand, the hypothesis that man is a special creation of an infinite workman, if true, does not enhance the mere a priori dignity of the human race. It may, and it will hereafter appear that it does, establish the moral accountability of man to a supreme being, a relation which, if I correctly understand the doctrine of evolution, is left out of the system that supposes intellect to be evolved out of the improving process by which matter becomes nervous organization, whose action exhibits those manifestations which we call mind. The moral accountability of man to a supreme being may, if it becomes established by proper evidence, be a circumstance that distinguishes him from other animals, and may, therefore, raise him in the scale of being. But then this dignity is a fact that comes after the process of reasoning has shown the relation of creator and creature, and it should not be placed at the beginning of the process among the proofs that are to show that relation. Mr. Darwin, in concluding his great work, "The Descent of Man," which he maintains to have been from some very low type of animated creature, through the apes, who became our ancestors, and who were developed into the lowest savages, and finally into the civilized man, has anticipated that his theory will, he regrets to say, be "highly distasteful to many"; and he adds, by way of parrying this disgust, that "he who has seen a savage in his native land will not feel much shame if forced to acknowledge that the blood of some more humble creature flows in his veins." For his own part, he adds, he would as soon be descended from a certain heroic little monkey who exposed himself to great danger in order to save the life of his keeper, as from a savage who delights to torture his enemies, offers bloody sacrifices, practices infanticide, etc. Waiving for the present the question whether the man who is called civilized is necessarily descended from or through the kind of savage whom Mr. Darwin saw in the Tierra del Fuego, or whether that kind of savage is a deteriorated offshoot from some higher human creatures that possessed moral and intellectual characteristics of a more elevated nature, I freely concede that this question of the dignity of our descent is not of much logical consequence. However distasteful to us may be the idea that we are descended from the same stock as the apes, and that their direct ancestors are to be traced to some more humble creature until we reach the lowest form of organized and animated matter, the dignity of our human nature is not to be reckoned among the probabilities by which our existence is to be accounted for. It is, in this respect, like the feeling or sentiment which prompts us to wish to find an infinite creator, the father of our spirits and the creator of our bodies. As a matter of reasoning, we must prove to ourselves, by evidence that satisfies the mind, that God exists. Having reached this conviction, the belief in his existence becomes a vast and inestimable treasure. But our wish to believe in God does not help us to attain that belief. In the same way our feeling about the dignity of man, the nobleness or ignobleness of our descent from or through one kind of creature or another, may be a satisfaction or a dissatisfaction after we have reached a conclusion, but it affords us no aid in arriving at a satisfactory conclusion from properly chosen premises.
And here, in advance of the tests which I shall endeavor to apply to the existence of God and the existence of man as a special creation, I desire to say something respecting the question of a logical antagonism between science and religion. I have often been a good deal puzzled to make out what those well-meaning persons suppose, who unwarily admit that there is no necessary antagonism between what modern science teaches and what religion teaches. Whether there is or is not, depends upon what we mean by science and religion. If by science we understand the investigation of Nature, or a study of the structure and conditions of everything that we can subject to the observation of our senses, and the deduction of certain hypotheses from what we observe, then we must compare the hypotheses with the teachings or conclusions which we derive from religion. The next question, therefore, is, What is religion? If we make it to consist in the Mosaic account of the creation, or in the teachings of the Bible respecting God, we shall find that we have to deal with more or less of conflict between the interpretations that are put upon a record supposed to have been inspired, and the conclusions of science. But if we lay aside what is commonly understood by revealed religion, which supposes a special communication from a superior to an inferior being of something which the former desires the latter to know, after the latter has been for some time in existence, then we mean by religion that belief in the existence of a superior being which we derive from the exercise of our reasoning powers upon whatever comes within the observation of our senses, and upon our own intellectual faculties. In other words, for what we call natural religion, we look both outward and inward, in search of a belief in a Supreme Being. We look outward, because the whole universe is a vast array of facts, from which conclusions are to be drawn; and among this array of facts is the construction of our bodies. We look inward, because our own minds present another array of facts from which conclusions are to be drawn. Now, if the conclusions which the scientist draws from the widest observation of Nature, including the human mind itself, fail to account for the existence of the mind of man, and natural religion does account for it, there is an irreconcilable conflict between science and religion. I can not avoid the conviction that Mr. Darwin has missed the point of this conflict. "I am aware," he says, "that the conclusions arrived at in this work will be denounced by some as highly irreligious; but he who denounces them is bound to show why it is more irreligious to explain the origin of man, as a distinct species by descent from a lower form, through the laws of variation and natural selection, than to explain the birth of the individual through the laws of ordinary reproduction." I do not understand him, by the terms "religious" or "irreligious," to refer to anything that involves praise or blame for adopting one hypothesis rather than another. I suppose he meant to say that a belief in his theory of the descent of man as a species is no more inconsistent with a belief in God than it is to believe that the individual is brought into being through the operation of the laws of ordinary reproduction which God has established. This would be strictly true, if the hypothesis of man's descent as a distinct species from some lower form accounted for his existence by proofs that satisfy the rules of evidence by which our beliefs ought to be and must be determined. In that case, there would be no inconsistency between his hypothesis and that to which natural religion conducts us. On the other hand, if the Darwinian hypothesis fails to establish a relation between the soul of man, as a special creation, and a competent creator, then the antagonism between this hypothesis and natural religion is direct, immediate, and irreconcilable; for the essence of religion consists in that relation, and a belief in that relation is what we mean, or ought to mean, by religion.
There is another form in which Mr. Darwin has depreciated the idea of any antagonism between his theory and our religious ideas, but it has the same logical defect as the suggestion which I have just considered, because it involves the same assumption. It is put hypothetically, but it is still an assumption, lacking the very elements of supreme probability that can alone give it force. "Man," he observes, "may be excused for feeling some pride at having risen, not through his own exertions, to the very summit of the organic scale; and the fact of his having so risen, instead of being aboriginally placed there, may give him some hope for a still higher destiny in the distant future." I certainly would not misrepresent, and I earnestly desire to understand, this distinguished writer. It is a little uncertain whether he here refers to the hope of immortality, or of an existence after the connection between our minds and our bodies is dissolved, or whether he refers to the further elevation of man on this earth in the distant future of terrestrial time. If he referred to the hope of an existence after what we call death, then he ought to have shown that his theory is compatible with such a continued existence of the soul of man. It will be one of the points on which I propose to bestow some attention, that the doctrine of evolution is entirely incompatible with the existence of the human soul for one instant after the brain has ceased to act as an organism, and death has wholly supervened; because that doctrine, if I understand it rightly, regards the intellect of man as a high development of what in other animals is called instinct, and instinct as a confirmed and inherited habit of animal organism to act in a certain way. If this is a true philosophical account of the origin and nature of intellect, it can have no possible individual existence after the organ called the brain, which has been in the habit of acting in a certain way, has perished, any more than there can be a digestion of food after the stomach or other assimilating organ has been destroyed. If, on the contrary, the mind of man is a special creation, of a spiritual essence, placed in an intimate union with the body for a temporary period, and made to depend for a time on the organs of that body as its means of manifestation and the exercise of its spiritual faculties, then it is conceivable that this union may be severed and the mind may survive. Not only is this conceivable, but, as I shall endeavor hereafter to show, the proof of it rises very high in the scale of probability—so high that we may accept it as a fact, just as confidently as we accept many things of which we can not have absolute certainty.
And here I think it needful, although not for all readers, but for the great majority, to lay down as distinctly as I can the rules of evidence which necessarily govern our beliefs. I do so because, in reading the works of many of the modern scientists who have espoused the Darwinian doctrine of evolution, I find that the rules of evidence are but little observed. There is a very great, often an astonishingly great, accumulation of facts, or of assumed facts. It is impossible not to be impressed by the learning, the industry, and the range of these writers. Nor would I in the least impugn their candor, or question their accuracy as witnesses of facts, which I am not competent to dispute if I were disposed to do so. But there is one thing for which I may suppose myself competent. I have through a long life been accustomed to form conclusions upon facts; and this is what every person does and must do who is asked to accept a new theory or hypothesis of any kind upon any subject.
Most of our beliefs depend upon what is called circumstantial evidence. There are very few propositions which address themselves to our belief upon one direct and isolated proof. We may class most of the perceptions of our senses among the simple and unrelated proofs which we accept without hesitation, although there is more or less of an unconscious and instantaneous process of reasoning, through which we pass before the evidence of our senses is accepted and acted upon. Then there are truths to which we yield an instant assent, because they prove themselves, as is the case with the mathematical or geometrical problems, as soon as we perceive the connection in the steps of the demonstration. Besides these, there are many propositions which, although they involve moral reasoning, have become axioms about which we do not care to inquire, but which we assume to have been so repeatedly and firmly established that it would be a waste of time to go over the ground again whenever they come up. But there is a very large class of propositions which address themselves to our belief, which do not depend on a single perception through our senses, and are not isolated facts, and are not demonstrable by mathematical truth, and are not axioms accepted because they were proved long ago, and have by general consent been adopted into the common stock of ideas. The class of beliefs with which the rules of circumstantial evidence are concerned are those where the truth of the proposition, or hypothesis, is a deduction from many distinct facts, but the coexistence of which facts leads to the inevitable conclusion that the proposition or hypothesis is true. We can not tell why it is that moral conviction is forced upon us by the coexistence of certain facts and their tendency to establish a certain conclusion. All we know is, that our minds are so constituted that we can not resist the force of circumstantial evidence if we suffer our faculties to act as reason has taught them. But, then, in any given case, whether we ought to yield our belief in anything where we have only circumstantial evidence to guide us, there are certain rules to be observed. The first of these rules is, that every fact in a collection of proofs from which we are to draw a certain inference must be proved independently by direct evidence, and must not be itself a deduction from some other fact. This is the first step in the process of arranging a chain of moral evidence. There is a maxim in this branch of the law of evidence that you can not draw an inference from an inference. In other words, you can not infer a fact from some other fact, and then unite the former with two or more independent facts to make a chain of proofs. Every link in the chain must have its separate existence, and its existence must be established by the same kind and degree of evidence as if it were the only thing to be proved. The next rule is to place the several facts, when so proved, in their proper relation to each other in the group from which the inference is to be drawn. In circumstantial evidence a fact may be established by the most direct and satisfactory proofs, and yet it may have no relation to other facts with which you attempt to associate it. For example, suppose it to be proved that A on a certain occasion bought a certain poison, and that soon after B died of that kind of poison; but it does not appear that A and B were ever seen together, or stood in any relation to each other. The fact that A bought poison would have no proper relation to the other fact that B died of that kind of poison. But introduce by independent evidence the third fact, that A knew B intimately, and then add the fourth fact, that A had a special motive for wishing B's death, you have some ground for believing that A poisoned B, although no human eye ever saw the poison administered. From this correlation of all the facts in a body of circumstantial evidence, there follows a third rule, namely, that the whole collection of facts, in order to justify the inference sought to be drawn from them, must be consistent with that inference. Thus, the four facts above supposed are entirely consistent with the hypothesis that A poisoned B. But leave out the two intermediate facts, or leave out the last one, and B might as well have been poisoned by C as by A. Hence there is a fourth rule: that the collection of facts from which an inference is to be drawn must not only be consistent with the probable truth of that inference, but they must exclude the probable truth of any other inference. Thus, not only must it be shown that A bought poison, that B died of poison, that A was intimate with B and had a motive for wishing B's death, but, to justify a belief in A's guilt, the motive ought to be shown to have been so strong as to exclude the moral probability that B was poisoned by some one else, or poisoned himself. It is in the application of these rules that in courts of justice the minds of jurymen often become perplexed with doubts which they can not account for, or else they yield a too easy credence to the guilt of the accused when the question of guilt depends upon circumstantial evidence.
I shall not spend much time in contending that these rules of evidence must be applied to scientific investigations which are to affect our belief in such a proposition as the descent of man from a common ancestor with the monkey. This is not only an hypothesis depending upon circumstantial evidence, but it is professedly a deduction from a great range of facts and from a very complex state of facts. In reasoning upon such subjects, when the facts which constitute the chain of circumstantial evidence are very numerous, we are apt to regard their greater comparative number as if it dispensed with a rigid application of the rules of determination. Every one can see, in the illustration above employed, borrowed from criminal jurisprudence, that the facts which constitute the chain of circumstantial evidence ought to be rigidly tested by the rules of determination before the guilt of the accused can be safely drawn as a deduction from the facts. But, in reasoning from physical facts to any given physical hypothesis where the facts are very numerous, there is a strong tendency to relax the rules of evidence, because, the greater the accumulation of supposed facts becomes, the greater is the danger of placing in the chain of evidence something that is not proved, and thus of vitiating the whole process. To this tendency, which I have observed to be very frequent among scientists, I should apply, without meaning any disrespect, the term invention. A great accumulation of facts is made, following one another in a certain order; all those which precede a certain intermediate link are perhaps duly and independently proved, and the same may be the case with those which follow that link. But there is no proof of the fact that constitutes the link and makes a complete chain of evidence. This vacuity of proof, if one may use such an expression, is constantly occurring in the writings of naturalists, and is often candidly admitted. It is gotten over by reasoning from the antecedent and the subsequent facts that the intermediate facts must have existed; and then the reasoning goes on to draw the inference of the principal hypothesis from a chain of proof in which a necessary intermediate link is itself a mere inference from facts which may be just as consistent with the non-existence as with the existence of the supposed intermediate link. In such cases we are often told very frankly that no one has yet discovered that the intermediate link ever actually existed; that the researches of science have not yet reached demonstrative proof of the existence of a certain intermediate animal or vegetable organization; that geological exploration has not yet revealed to us all the specimens of the animal or vegetable kingdoms that may have inhabited this globe at former periods of time; but that the analogies which lead down or lead up to that as yet undiscovered link in the chain are such that it must have existed, and that we may confidently expect that the actual proof of it will be found hereafter. The difficulty with this kind of reasoning is that it borrows from the main hypothesis which one seeks to establish the means of showing the facts from which the hypothesis is to be drawn as an inference. Thus, for example, the hypothesis is that the species called man is a highly developed animal formed by a process of natural selection that went on for unknown ages among the individuals descended from the progenitor of the anthropomorphous apes. The facts in the physical organization and mental manifestations of the animal called man, when viewed historically through all the conditions in which we know anything of this species, lead up to that common supposed ancestor of the apes. The facts in the physical organization and instinctive habits of the ape, when viewed historically through all the conditions in which we know anything of his species, show that he, too, was evolved by the process of natural selection out of that same ancestor. Intermediate, respectively, between the man and the monkey and their primordial natural-selection ancestor or predecessor, there are links in the chain of proof of which we have no evidence, and which must be supplied by inferring their existence from the analogies which we can trace in comparing things of which we have some satisfactory proof. Thus, the main hypothesis, the theory of natural selection as the explanation of the existence of distinct species of animals, is not drawn from a complete chain of established facts, but it is helped out by inferring from facts that are proved other facts that are not proved, but which we have reason to expect will be discovered hereafter. I need not say that this kind of argument will not do in the common affairs of life, and that no good reason can be shown why our beliefs in matters of science should be made to depend upon it.
We do not rest our belief in what is called the law of gravitation upon any chain of proof in which it is necessary to supply a link by assuming that it exists. The theory that bodies have a tendency to approach each other, that the larger mass attracts to itself the smaller by a mysterious force that operates through all space, is a deduction from a great multitude of perpetually recurring facts that are open to our observation, no one of which is inferred from any other fact, while the whole excludes the moral probability that any other hypothesis will account for the phenomena which are continually and invariably taking place around us.
This illustration of the rules of evidence, when applied to scientific inquiries, leads me to refer to one of the favorite postulates of the evolution school. We are often told that it ought to be no objection to the doctrine of evolution that it is new, or startling, or contrary to other previous theories of the existence of species. We are reminded again and again that Galileo's grand conception was scouted as an irreligious as well as an irrational hypothesis, and that the same reception attended the first promulgation of many scientific truths which no intelligent and well-informed person now doubts.[2] Then we have it asserted that the doctrine of evolution is now accepted by nearly all the most advanced and accomplished natural philosophers, especially those of the rising scientists who have bestowed most attention upon it. Upon this there are two things to be said: First, it is a matter of very little consequence that the learned of a former age did not attend to the proofs of the law of gravitation, or of any other new theory of physics, as they should have done, and that they consequently rejected it. Their logical habits of mind, their preconceived religious notions, and many other disturbing causes, rendered them incapable of correct reasoning on some particular subject, while they could reason with entire correctness on other subjects. Secondly, the extent to which a new theory is accepted by those whose special studies lead them to make the necessary investigations, does not dispense with the application of the laws of evidence to the facts which are supposed to establish the theory. The doctrine of evolution addresses itself not only to the scientific naturalist, but to the whole intelligent part of mankind. How is one who does not belong to this class of investigators to regulate his belief in the theory which they propound? Is he to take it on their authority? or is he, while he accords to their statements of facts all the assent which as witnesses they are entitled to expect from him, to apply to their deduction the same principles of belief that he applies to everything else which challenges belief, and to assent or dissent accordingly? No one, I presume, will question that the latter is the only way in which any new matter of belief should be approached. I have not supposed that any scientist questions this; but I have referred to the constant iteration that the doctrine of evolution is now generally admitted by men of science, that the assertion, supposing it to be true, may pass for just what it is worth. It is worth this and no more: that candid, truthful, and competent witnesses, when they speak of facts that they have observed, are entitled to be believed as to the existence of those facts. When they assume facts which they do not prove, but which are essential links in the chain of evidence, or when the facts which they do prove do not rationally exclude every other hypothesis excepting their own, the authority of even the whole body of such persons is of no more account than that of any other class of intelligent and cultivated men. In the ages when ecclesiastical authority exercised great power over the beliefs of men upon questions of physical science, the superiority was accorded to the authority which claimed it, and the scientist who propounded a new physical theory that did not suit the theologian was overborne. It seems to me that it is a tendency of the present age to substitute the authority of scientific experts in the place of the ecclesiastical authority of former periods, by demanding that something more than the office of witnesses of facts shall be accorded to them. We are told that it is a very important proof of the soundness of deductions, that the deductions are drawn by the greater number of the specialists who have examined the facts. Sometimes this is carried so far as to imply presumption in those who do not yield assent to the theory, as if it ought to be accepted upon the authority of the experts whose proper office it is to furnish us with the facts, and whose deductions we have to examine upon the strength of their reasoning. Those of us who are not professors of the particular science may be charged with ignorance or incapacity if we do not join in the current of scientific opinion. But, after all, the new theory challenges our belief. If we examine it at all, we must judge of it, not by the numbers of those who propound or accept it, or by any amount of mere authority, but by the soundness of the reasoning by which its professors support it.
The reader is now informed of what he may expect to find discussed in this volume. It remains for me to indicate the mode in which the discussion will be carried on. I propose to divest my own mind, and so far as I may to divest the mind of the reader, of all influence from revealed religion. I shall not refer to the Mosaic account of the creation excepting as I refer to other hypotheses. With its authority as an account given by the Deity himself through his chosen servant, I have here nothing to do. Nor shall I rely upon the revelation recorded in the New Testament. All the inquiries which I propose to make are those which lie in the domain of natural religion; and while I can not expect, in exploring this domain, to make discoveries or to find arguments which can claim the merit of originality, I may avoid traveling in a well beaten path, by pursuing the line of my own reflections, without considering whether they coincide with or differ from the reasonings of others. Although, at a former period of my life, I have studied the great writers whose speculations in the science of natural theology are the most famous and important pieces in its literature, it is more than forty years since I have looked into one of them; and I do not propose to turn to them now, in order to see whether they have or have not left any traces in my mind. It is quite possible that critics may array against me the authority of some great name or names; but even if I am to be charged with presumption in entering upon this field, it will not be found, so far as I am conscious, that I have borrowed an argument, imitated a method, or followed an example.