Nature and importance of the subject—Is there a relation of Creator and creature between God and man?—Rules of rational belief—Is natural theology a progressive science?

Man finds himself in the universe a conscious and thinking being. He has to account to himself for his own existence. He is impelled to this by an irresistible propensity, which is constantly leading him to look both inward and outward for an answer to the questions: What am I? How came I to be? What is the limit of my existence? Is there any other being in the universe between whom and myself there exists the relation of Creator and creature?

The whole history of the human mind, so far as we have any reliable history, is marked by this perpetual effort to find a First Cause.

However wild and fantastic may be the idea which the savage conceives of a being stronger and wiser than himself; however groveling and sensual may be his conception of the form, or attributes, or action of that being, he is, when he strives after the comprehension of his deity, engaged in the same intellectual effort that is made by the most civilized and cultivated of mankind, when, speculating upon the origin of the human soul, or its relation to the universe, or the genesis of the material world, they reach the sublime conception of an infinite God, the creator of all other spiritual existences and of all the forms of animal life, or when they end in the theory that there is no God, or in that other theory which supposes that what we call the creation, man included, is an evolution out of primordial matter, which has been operated upon by certain fixed laws, without any special interposition of a creating power, exerted in the production of the forms of animal life that now inhabit this earth, or ever have inhabited it. In the investigation of these contrasted theories, it is necessary to remember that the faculties of the human mind are essentially the same in all conditions of civilization or barbarism; that they differ only in the degree of their growth, activity, and power of reasoning, and therefore that there must be a common standard to which to refer all beliefs. The sole standard to which we can refer a belief in anything is its rationality, or a comparison between that which is believed and that which is most probable, according to the power of human reason to weigh probabilities. In the untutored and uncultivated savage, this power, although it exists, is still very feeble; partly because it is exercised upon only a few objects, and partly because the individual has comparatively but little opportunity to know all the elements which should be taken into account in determining a question of moral probabilities.

In the educated and cultivated man this power of judging probabilities, of testing beliefs by their rationality, is carried, or is capable of being carried, to the highest point of development, so as to comprehend in the calculation the full elements of the question, or at least to reduce the danger of some fatal omission to the minimum. It is, of course, true that the limited range of our faculties may prevent a full view of all the elements of any question of probability, even when our faculties have attained the highest point of development experienced by the age in which we happen to live. This renders the rationality of any hypothesis less than an absolutely certain test of truth. But this rationality is all that we have to apply to any question of belief; and if we attend carefully to the fact that moral probabilities constitute the groundwork of all our beliefs, and note the mental processes by which we reach conclusions upon any question depending upon evidence, we shall find reason to regard this power of testing beliefs by a conformity between the hypotheses and that which is most probable to be the most glorious attribute of the human understanding, as it is unquestionably the safest guide to which we can trust ourselves.

It may be that, while philosophers will not object to my definition of rationality, churchmen will ask what place I propose to assign to authority in the formation of beliefs. I answer, in the first place, that I am seeking to make myself understood by plain but reflecting and reasoning people. Such persons will perceive that what I mean by the rationality of a belief in any hypothesis is its fitness to be accepted and acted upon because it has in its favor the strongest probabilities of the case, so far as we can grasp those probabilities. I know of no other foundation for a belief in anything; for belief is the acceptance by the mind of some proposition, statement, or supposed fact, the truth of which depends upon evidence addressed to our senses, or to our intellectual perceptions, or to both. In the next place, in regard to the influence of authority over our beliefs, it is to be observed that the existence of the authority is a question to be determined by evidence, and this question, therefore, of itself involves an application of the test of rationality, or conformity with what is probable. But, assuming that the authority is satisfactorily established, it is not safe to leave all minds to the teaching of that authority, without the aid of the reasoning, which, independent of all authority, would conduct to the same conclusion. There are many minds to whom it is useless to say, You are commanded to believe. The question instantly arises, Commanded by whom, or what? And if the answer is, By the Church, or by the Bible, and the matter is left to rest upon that statement, there is great danger of unbelief. It is apparent that a large amount of what is called infidelity, or unbelief, now prevailing in the world, is due to the fact that men are told that they are commanded to believe, as if they were to be passive recipients of what is asserted, and because so little is addressed to their understandings.

I do not wish to be understood as maintaining that there is no place for authority in matters of what is called religious belief. I am quite sensible that there may be such a thing as authority even in regard to our beliefs; that it is quite within the range of possibilities that there should be such a relation between the human soul and an infinite Creator as to require the creature to accept by faith whatever a proved revelation requires that intelligent creature to believe. But, in view of the fact that what is specially called revealed religion is addressed to an intelligent creature, to whom the revelation itself must be proved by some evidence that will satisfy the mind, there is an evident necessity for treating the rationality of a belief in God as an independent question. In some way, by some process, we must reach a belief in the existence of a being before we can consider the claims of a message which that being is supposed to have sent to us. What we have to work with, before we can approach the teaching of what is called revealed religion, is the mind of man and the material universe. Do these furnish us with the rational basis for a belief in God?

And here I shall be expected to say what I mean by a belief in God. I have neither so little reverence for what I myself believe in, nor so little respect for my readers, as to offer them anything but the common conception of God. All that is necessary for me to do, in order to put my own mind in contact with that of the reader, is to express my conception of God just as it would be expressed by any one who is accustomed to think of the being called God by the Christian, the Jew, the Mohammedan, or by some other branches of the human race. These different divisions of mankind may differ in regard to some of the attributes of the Deity, or his dealings with men, or the history or course of his government of the world. But what is common to them all is a belief in God as the Supreme Being, who is self-existing and eternal, by whose will all things and all other beings were created, who is infinite in power and wisdom and in goodness and benevolence. As an intellectual conception, this idea of a Supreme Being, one only God, who never had a beginning and can have no end, and who is the creator of all other beings, excludes, of course, the polytheism of the ancient civilized nations, or that of the present barbarous tribes; and it especially excludes the idea of what the Greeks called Destiny, which was a power that governed the gods as well as the human race, and was anterior and superior to Jove himself. The simple conception of the one God held by the Christian, the Jew, or the Mohammedan, as the First Cause of the universe and all that it embraces, creating all things and all other beings by his will, in contrast with the modern idea that they came into existence without the volition of a conscious and intelligent being making special creations, is what I present to the mind of the reader.

This idea of God as a matter of belief presents, I repeat, a question of moral probabilities. The existence of the universe has to be accounted for somehow. We can not shut out this inquiry from our thoughts. The human being who never speculates, never thinks, upon the origin of his own soul, or upon the genesis of this wondrous frame of things external to himself, or upon his relations to some superior being, is a very rare animal. If he is much more than an animal, he will have some idea of these things; and the theories by which some of the most cultivated and acute intellects of our race, from the widest range of accumulated physical facts and phenomena yet gathered, have undertaken to account for the existence of species without referring them to the volition of an infinite creator, are at once a proof of the universal pressure of the question of creation upon the human mind, and of the logical necessity for treating it as a question dependent upon evidence and probability.

I lay out of consideration, now, the longing of the human mind to find a personal God and Creator. This sentiment, this yearning for an infinite father, this feeling of loneliness in the universe without the idea of God, is certainly an important moral factor in the question of probability; but I omit it now from the number of proofs, because it is a sentiment, and because I wish to subject the belief in God as the Creator to the cold intellectual process by which we may discover a conformity between that hypothesis and the phenomena of Nature as a test of the probable truth. If such a conformity can be satisfactorily shown, and if the result of the process as conducted can fairly claim to be that the existence of God the Creator has by far the highest degree of probability above and beyond all other hypotheses that have been resorted to to account for our existence, the satisfaction of a moral feeling of the human heart may well become a source of happiness, a consolation in all the evils of this life, and a support in the hour of death.

But in this preliminary chapter I ought to state what I understand to be the scientific hypothesis or hypotheses with which I propose to contrast the idea of God as the creator of species by applying the test of probability. To discuss the superior claims of one hypothesis over another, without showing that there is a real conflict between them, would be to set up a man of straw for the sake of knocking it down as if it were a living and real antagonist. What I desire to do is not to aim at a cheap victory by attacking something that does not call for opposition; but it is to ascertain first whether there is now current any explanation or hypothesis concerning the origin of the creation, or anything that it contains, which rejects the idea of God as the creator of that which we know to exist and as it exists, and then to ascertain which of the two hypotheses ought to be accepted as the truth, because it has in its favor the highest attainable amount of probability. There is an amount of probability which becomes to us a moral demonstration, because our minds are so constituted that conviction depends upon the completeness with which the evidence in favor of one hypothesis excludes the other from the category of rational beliefs.

I pass by the common sort of infidelity which rejects the idea of an intelligent creator acting in any manner whatever, whether by special creations or by laws of development operating on some primordial form of animal life. But among the modern scientists who have propounded explanations of the origin of species, I distinguish those who do not, as I understand, deny that there was an intelligent Creator by whose will some form of animal life was originally called into being, but who maintain that the diversified forms of animal life which we now see were not brought into being by the special will of the Creator as we now know them, but that they were evolved, by a process called natural selection, out of some lower type of animated organism. Of this class, the late Mr. Darwin is a representative. There is, however, at least one philosopher who carries the doctrine of evolution much farther, and who, if I rightly understand him, rejects any act of creation, even of the lowest and simplest type of animal existence. This is Mr. Herbert Spencer—a writer who, while he concurs in Mr. Darwin's general theory of natural selection as the process by which distinct organisms have been evolved out of other organisms, does not admit of any primal organism as the origin of the whole series of animals and as the creation of an intelligent will.

It will be appropriate hereafter to refer to the doctrine of evolution as a means of accounting for the existence of the human mind. At present it is only necessary to say that I understand it to be maintained as the hypothesis which has the highest attainable amount of evidence in its favor, that distinct species of animals are not a creation but a growth; and also that the mind of man is not a special creation of a spiritual existence, but a result of a long process by which organized matter has slowly worked itself from matter into intellect. Wherever, for instance, these scientists may place the non-human primate, out of which man has been evolved by what is called natural selection, and whether they do or do not assume that he was a creation of an intelligent will, they do not, as I understand, claim that the primate was endowed with what we call intellect; so that at some time there was a low form of animal life without intellect, but intellect became evolved in the long course of countless ages, by the process of natural selection, through the improving conditions and better organization of that low animal which had no intellect. In other words, we have what the scientist calls the non-human primate, a low form of animal without intellect, but capable of so improving its own physical organization as to create for itself and within itself that essence which we recognize as the human mind. Here, then, there is certainly a theory, an hypothesis, which may be and must be contrasted with the idea that the mind of man is a spiritual essence created by the volition of some other being having the power to create such existences, and put into a temporary union with a physical organization, by the establishment of a mysterious connection which makes the body the instrument of the soul so long as the connection exists. If I have stated correctly the theory which assigns the origin of the human mind to the process of evolution, I have assuredly not set up a man of straw. I stand confronted with an hypothesis which directly encounters the idea that the human intellect is a creation, in the sense of a direct, intelligent, conscious, and purposed production of a special character, as the human mind and hand, in the production of whatever is permitted to finite capacities, purposely creates some new and independent object of its wishes, its desires, or its wants. The human mind, says the scientist, was not created by a spiritual being as a spiritual existence independent of matter, but it grew out of matter, that was at first so organized that it did not manifest what we call intellect, but that could so improve its own organization as to evolve out of matter what we know as mind.

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.

There is a passage in one of the writings of Lord Macaulay in which that brilliant essayist maintained that natural theology is not a progressive science. Macaulay's tendency to paradox was often aggravated by the superficial way in which he used his multifarious knowledge. As in the course of this work I am about to do that which he regarded as idle, namely, to inquire whether natural religion, aside from revelation, is of any value as a means of reaching a belief in the existence and attributes of God and the immortality of man, I cite the passage in which Macaulay makes the assertion that natural theology has made no progress from the time of the Greek philosophers to the present day: "As respects natural religion, revelation being for the present altogether left out of the question, it is not easy to see that a philosopher of the present day is more favorably situated than Thales or Simonides. He has before him just the same evidences of design in the structure of the universe that the early Greeks had. We say just the same, for the discoveries of modern astronomers and anatomists have really added nothing to the force of that argument which a reflecting mind finds in every beast, bird, insect, fish, leaf, flower, and shell. The reasoning by which Socrates in Xenophon's hearing confuted the little atheist Aristophanes, is exactly the reasoning of Paley's 'Natural Theology.' Socrates makes precisely the same use of the statues of Polycletus and the pictures of Zeuxis which Paley makes of the watch. As to the other great question, the question what becomes of man after death, we do not see that a highly educated European, left to his unassisted reason, is more likely to be in the right than a Blackfoot Indian. Not a single one of the many sciences in which we surpass the Blackfoot Indians throws the smallest light on the state of the soul after the animal life is extinct. In truth, all the philosophers, ancient and modern, who have attempted without the aid of revelation to prove the immortality of man, from Plato down to Franklin, appear to us to have failed deplorably.

"Then, again, all the great enigmas which perplex the natural theologian are the same in all ages. The ingenuity of a people just emerging from barbarism is quite sufficient to propound those enigmas. The genius of Locke or Clarke is quite unable to solve them. It is a mistake to imagine that subtile speculations touching the Divine attributes, the origin of evil, the necessity of human actions, the foundation of moral obligation, imply any high degree of intellectual culture. Such speculations, on the contrary, are in a peculiar manner the delight of intelligent children and of half-civilized men. The number of boys is not small who, at fourteen, have thought enough on these questions to be fully entitled to the praise which Voltaire gives to Zadig: 'Il en savait ce qu'on a su dans tous les ages; c'est À dire, fort peu de chose.'

"The book of Job shows that, long before letters and arts were known to Ionia, these vexing questions were debated with no common skill and eloquence under the tents of the Idumean emirs; nor has human reason, in the course of three thousand years, discovered any satisfactory solution of the riddles which perplexed Eliphaz and Zophar. Natural theology, then, is not a progressive science."[3]

Here, in the space of two not very long paragraphs, is a multitude of allusions which evince the range of Lord Macaulay's reading, but which are employed, without very close thinking, in a quite inaccurate way, to sustain assertions that are not true. If he had said that a modern philosopher has before him in the structure of the universe not only all the same evidence of design which the early Greeks had, but a great deal more, he would have hit the exact truth. It is simple extravagance to say that modern astronomy has added nothing to the strength of the argument which shows the existence of a supreme lawgiver and artificer of infinite power and skill. What did the early Greeks know about the structure of the solar system, the law of universal gravitation, and the laws of motion? Compare the ideas entertained by the Greek philosophers of the phenomena of the universe with those which modern astronomy has enabled a modern philosopher to assume as scientific facts established by rigorous demonstration; compare what was known before the invention of the telescope with what the telescope has revealed; compare the progress that was made in Greek speculative philosophy from the time of Thales to the time of Plato, and then say whether natural religion had not made advances of the greatest importance even before modern science had multiplied the means for still greater progress. A brief summary of the Greek philosophy concerning the producing causes of phenomena will determine whether Lord Macaulay was right or wrong in the assertion that the "early Greeks" had as good means of making true deductions in natural theology as the means which exist to-day.

All scholars who have attended to the history of Greek speculation know that the Greeks held to the belief in polytheistic personal agents as the active producers of the phenomena of Nature. This was the system of Homer and Hesiod and the other old poets. This was the popular belief held throughout all the Hellenic world, and it continued to be the faith of the general public, not only after the different schools of philosophy had arisen, but down to and after the time when St. Paul stood on Mars Hill and told the men of Athens how he had found that they were in all things too superstitious. Thales, who flourished in the first half of the sixth century before Christ, was the first Greek who suggested a physical agency in place of a personal. He assumed the material substance, water, to be the primordial matter and universal substratum of everything in Nature. All other substances were, by transmutations, generated from water, and when destroyed they all returned into water. His idea of the earth was that it was a flat, round surface floating on the immense watery expanse or ocean. In this he agreed with the old poets; but he did not, like them, suppose that the earth extended down to the depths of Tartarus. The Thalesian hypothesis, therefore, rejected the Homeric Okeanus, the father of all things, and substituted for that personal agency the agency of one primordial physical substance, by its own energy producing all other substances. This is about all that is known of the philosophy of Thales, and even this is not known from any extant writing of his, but it is derived from what subsequent writers, including Aristotle, have imputed to him.[4] Why Lord Macaulay should have selected Thales as the Greek philosopher who was as favorably situated as a philosopher of the present day for dealing with questions of natural religion, is not very apparent. All that Thales did, assuming that we know what he did, was to strike out a new vein of thought, the direct opposite of the poetical and popular idea of the origin of phenomena.

From Thales to Plato, a century and a half intervened.[5] During this period there arose, according to Mr. Grote, twelve distinct schemes of philosophy, the authors of which that learned Englishman has enumerated, together with an admirable summary of their respective systems. From this summary certain things are apparent. All these philosophers, from Thales to Democritus, while each speculated upon Nature in an original vein of his own, endeavored to find an explanation or hypothesis on which to account for the production and generation of the universe by some physical agency apart from the mythical personifications which were believed in by the populace and assumed in the poetical theologies. Some of them, without blending ethics and theology in their speculations, adopted, as the universal and sufficient agents, the common, familiar, and pervading material substances, such as water, fire, air, etc.; others, as Pythagoras and his sect, united with ethical and theological speculations the idea of geometrical and arithmetical combinations as the primal scientific basis of the phenomena of Nature. But what was common to all these speculations was the attempt to find a scientific basis on which to explain, by physical generation, by transmutation and motion from place to place, the generation of the Kosmos, to take the place of generation by a divine personal agency or agencies. But while these speculations were of course unsuccessful, their abundance and variety, the inventive genius which they exhibit, the effort to find a scientific basis apart from the popular and poetic belief in a multitude of personal and divine agencies, constitute, as Mr. Grote has well said, "one of the most memorable facts in the history of the Hellenic mind"; and "the mental effort required to select some known agency and to connect it by a chain of reasoning with the result, all this is a new phenomenon in the history of the human mind." Such an amount of philosophical speculations could not go on for a century and a half without enlarging the means for dealing with questions of natural theology; for they very nearly exhausted the "causings and beginnings" which could be assigned to regular knowable and predictable agencies; and these they carried through almost every conceivable form of action by which such agencies could be supposed to operate. While the authors of these systems of philosophy were constantly hampered by the popular and poetic conceptions of a diversified and omnipresent polytheistic agency, a belief which, as Mr. Grote has said, was "eminently captivating and impressive," and which pervaded all the literature of their time, their speculations accumulated a vast fund of ideas in the sphere of scientific explanations, which, although unsatisfactory to modern science, became, when we reach Plato, the principal influence which led him to revert to the former idea of a divine agency, intentionally and deliberately constructing out of a chaotic substratum the system of the Kosmos; and which also led him to unite with it the idea of a mode in which it acted on and through the primordial elements of matter.

So that, from the class of philosophers to whom Lord Macaulay presumably referred as "the early Greeks," down to and including Plato, there was a great advance. The earlier Greek philosophers did not divide substance from its powers or properties, nor did they conceive of substance as a thing acted upon by power, or of power as a thing distinct from substance. They regarded substance, some primordial substance, with its powers and properties, as an efficient and material cause, and as the sole cause, as a positive and final agent. They did not seek for a final cause apart from the substances which they supposed to be the sole agents operating to produce important effects. But, inasmuch as they carried their various theories through nearly the whole range of possible speculation, they enabled Plato and Aristotle to see that there was a fundamental defect in their reasoning; that there must be an abstract conception of power as something distinct from substance or its properties. It was by Plato and Aristotle that this abstract conception was reached, of course without any influence of what we regard as revelation; and, although they did not always describe correctly the mode in which this power had acted, their perception of the logical necessity for such a final cause marks a great progress in philosophical speculation. It entirely refutes Lord Macaulay's assertion that natural theology is not a progressive science. It had made great progress from Thales to Plato; and while in a certain sense it is true that "a modern philosopher has before him just the same evidence of design in the structure of the universe which the early Greeks had"—that is, he has the same physical phenomena to observe—it is not true that the early Greeks did not develop conceptions of the origin of the universe valuable to their successors. Lord Macaulay should not have compared Thales with the modern philosopher, in respect of advantage of situation, but he should have compared the modern philosopher with Plato, and Plato with his predecessors; and if he had done this, he could not have asserted with any show of truth that natural theology has made no advance as a science from the time of Thales, the Milesian philosopher, and Simonides, the poet, to the present day. I shall have occasion hereafter to speak of the masterly intellectual power by which Plato wrought out his conception of a formative divine agency in the production of the Kosmos, and the bold and original speculation by which he avoided the charge of infidelity toward the established religion of his countrymen.

When I come to speak of what modern astronomy has done in furnishing us with new means of sound philosophical speculation on the being, attributes, and methods of God, it will be seen whether Lord Macaulay is correct in the assertion that it has added nothing to the argument. At present I will briefly advert to what the "early Greeks," or any of the Greeks, knew of the structure of the solar system. We learn, from a work which dates from nearly the middle of the second century of the Christian era, what was the general conception of the solar system among the ancients, including the Greeks. This work is known as the "Almagest" of Ptolemy, and the name of the "Ptolemaic System" has been given to the theory which he describes. This theory was common to all the ancient astronomers, Ptolemy's statement of it being a compendium of what they believed. Its principal features are these: 1. The heavens are a vast sphere, in which the heavenly bodies are set, and around the pole of this sphere they revolve in a circle every day. 2. The earth is likewise a sphere, and is situated in the center of the celestial plane as a fixed point. The earth having no motion, and being in the center of all the motions of the other bodies, the diurnal revolutions of those bodies are in a uniform motion around it. 3. The sun, being one of the heavenly bodies making a revolution around the earth, was supposed to be placed outside of the position of Venus in the heavenly sphere. The order of the Ptolemaic system was thus: The moon was first, being nearest to the earth; then came Mercury and Venus, the sun being between Venus and Mars. Beyond Mars came Jupiter and Saturn. Plato's arrangement was in one respect different, his order being the moon, the sun, Mercury, Venus, Mars, Jupiter, and Saturn. But this ideal heavenly sphere, with the earth in the center of all the revolutions of the other bodies, and remaining quiescent—a theory which was common to all the ancient astronomers—was the result of observing the motions of the heavenly bodies as they appear to a spectator on the earth. Such a spectator would have this appearance of a celestial sphere presented to him wherever he might be; and, judging from the apparent motions of the heavenly bodies relative to his own position at the center, he would conclude that the earth is at that center, and that it remains at rest, supported on nothing. It required certain discoveries to explode this system of a celestial sphere. First came Copernicus, who, about the middle of the sixteenth century of our era, published his demonstrations, which convinced the world of two great propositions: 1. That the diurnal revolution of the heavens is nothing but an apparent motion, caused by the revolution of the earth on its own axis. 2. That the earth is but one of a group of planets, all of which revolve around the sun as a center. Next came Kepler, who, in the early part of the seventeenth century, recognizing the truth of the Copernican system, determined the three laws of planetary motion: 1. That the orbit of each planet is an ellipse, the sun being in one focus. 2. That as each planet moves around the sun, the line which joins it to the sun passes over equal areas in equal times. 3. That the square of the time of a planet's revolution around the sun is in proportion to the cube of its mean distance from the sun. These laws were discovered by Kepler as deductions made upon mathematical principles from observations which had to be carried on without the aid of the telescope, and without that knowledge of the general laws of motion which came later. Kepler's laws, although in the main correct, were subsequently found to be subject to certain deviations in the planetary motions. It was when Galileo, the contemporary of Kepler, who, if he was not the first inventor of the telescope, was the first to use it in astronomical observations, was able by means of it to discover the general laws of motion, that the substantial accuracy of Kepler's three laws could be proved, while at the same time the deviations from them were accounted for. Still, there was wanting the grand discovery, which would disclose the cause of these motions of the planets in elliptical orbits, and the relations between their distances and their times of revolution, and thus reduce the whole of the phenomena to a general law. Descartes, who flourished 1596-1650, first attempted to do this by his theory of Vortices. He supposed the sun to be immersed in a vast fluid, which, by the sun's rotation, was made to rotate in a whirlpool, that carried the planets around with it, the outer ones revolving more slowly because the parts of the ethereal fluid in which they were immersed moved more slowly. This was a reversion back to some of the ancient speculations. It was reserved for Newton to discover the law of universal gravitation, by which, in the place of any physical connection between the bodies of the solar system by any intervening medium, the force of attraction exerted by a larger body upon a smaller would draw the smaller body out of the straight line that it would pursue when under a projectile force, and would thus convert its motion into a circular revolution around the attracting body, and make the orbit of this revolution elliptical by the degree in which the attracting force varied in intensity according to the varying distance between the two bodies. When Newton's laws of motion were discovered and found to be true, the phenomena of the solar system were explained.

It may be interesting, before leaving for the present this branch of the subject, to advert more particularly to one of the philosophical systems of the Greeks, which, when compared with the discoveries of modern astronomy, illustrates the great addition that has been made to our means of sound speculation upon the origin of the material universe. I refer to the system of the Pythagoreans—one of the most remarkable instances of the invention of facts to fit and carry out a theory that can be found in the history of philosophy, although we are not without striking examples of this practice in modern speculations. It has already been seen that, during the whole period of Greek philosophy before the time of Plato, the problem was to find a primordial and universal agent by which the sensible universe was built up and produced; supplying, that is to say, the matter and force required for the generation of successive products.[6] It has been seen that the Thalesian philosophers undertook to solve this problem by the employment of some primordial physical substance, such as water, fire, air, etc. Pythagoras and his school held that the essence of things consisted in number; by which they did not mean simply that all things could be numbered, but they meant that numbers were substance, endowed with an active force, by which things were constituted as we know them. In the Pythagorean doctrine number was the self-existing reality; not, as in Plato's system of ideas, separate from things, but as the essence or determining principles of things, and having, moreover, magnitude and active force.[7] This remarkably subtle conception of an agent in the production of material things evinces the effort that was making, in a direction opposite to that of Thales and his immediate successors, to find a First Cause. It was carried out by the Pythagoreans in the movements of the heavenly bodies, in the works of human art, and in musical harmony; in all of which departments, according to Mr. Grote, they considered measure and number as the producing and directing agencies. We are here concerned only with their application of this theory to the celestial bodies. One of their writers is quoted by Mr. Grote as a representative of the school which was founded by Pythagoras (about 530 B. C.), and which extended into the GrÆco-Italian cities, where, as a brotherhood, they had political ascendency until they were put down and dispersed about 509 B. C.; but they continued for several generations as a social, religious, and philosophical sect. According to this writer (Philolaus), "the Dekad, the full and perfect number, was of supreme and universal efficacy as the guide and principle of life, both to the Kosmos and to man. The nature of number was imperative and law-giving, affording the only solution of all that was perplexing or unknown; without number all would be indeterminate and unknowable."

Accordingly, the Pythagoreans constructed their system of the universe by the all-pervading and producing energy of this primordial agent, Number, in the manner thus described by Mr. Grote (i, 12-15): "The Pythagoreans conceived the Kosmos, or the universe, as one single system, generated out of numbers. Of this system the central point—the determining or limiting One—was first in order of time and in order of philosophical conception. By the determining influence of this central constituted One, portions of the surrounding Infinite were successively attracted and brought into system: numbers, geometrical figures, solid substances were generated. But, as the Kosmos thus constituted was composed of numbers, there could be no continuum; each numeral unit was distinct and separate from the rest by a portion of vacant space, which was imbibed, by a sort of inhalation, from the infinite space or spirit without. The central point was fire, called by the Pythagoreans the Hearth of the Universe (like the public hearth or perpetual fire maintained in the prytaneum of a Grecian city), or the watch-tower of Zeus. Around it revolved, from west to east, ten divine bodies, with unequal velocities, but in symmetrical movement or regular dance. Outermost was the circle of the fixed stars, called by the Pythagoreans Olympus, and composed of fire like the center. Within this came successively, with orbits more and more approximating to the center, the five planets, Saturn, Jupiter, Mars, Venus, Mercury; next, the sun, the moon, and the earth. Lastly, between the earth and the central fire, an hypothetical body, called the Antichthon, or counter-earth, was imagined for the purpose of making up a total represented by the sacred number ten, the symbol of perfection and totality. The Antichthon was analogous to a separated half of the earth, simultaneous with the earth in its revolutions, and corresponding with it on the opposite side of the central fire. The inhabited portion of the earth was supposed to be that which was turned away from the central fire and toward the sun, from which it received light. But the sun itself was not self-luminous: it was conceived as a glassy disk, receiving and concentrating light from the central fire, and reflecting it upon the earth, so long as the two were on the same side of the central fire. The earth revolved in an orbit obliquely intersecting that of the sun, and in twenty-four hours, round the central fire, always turning the same side toward that fire. The alternation of day and night was occasioned by the earth being, during a part of such revolution, on the same side of the central fire with the sun, and thus receiving light reflected from him; and during the remaining part of her revolution on the side opposite to him, so that she received no light at all from him. The earth, with the Antichthon, made this revolution in one day; the moon, in one month; the sun, with the planets Mercury and Venus, in one year; the planets Mars, Jupiter, and Saturn in longer periods respectively, according to their distances from the center; lastly, the outermost circle of the fixed stars (the Olympus, or the Asslanes), in some unknown period of very long duration.

"The revolutions of such grand bodies could not take place, in the opinion of the Pythagoreans, without producing a loud and powerful sound; and as their distances from the central fire were supposed to be arranged in musical ratios, so the result of all these separate sounds was full and perfect harmony. To the objection, Why were not the sounds heard by us? they replied that we had heard them constantly and without intermission from the hour of our birth; hence they had become imperceptible by habit."

Beautiful as was this theory—the origin of the phrase, "the music of the spheres"—it owed its perfection as a theory to a pure invention, resorted to in order to carry out the hypothesis of the sacred number Ten, of which all the greater numbers were only compounds and derivatives. This perfect and normal Ten, as a basis on which to rest a bold astronomical hypothesis, required the imagination of the Antichthon, or counter-earth, in order, with the other bodies, to make up the primordial number to whose generative force the whole of these bodies owed their origin. The resort to this conception of number, as a formative and active agent, was doubtless due to the fact that the Pythagoreans were the earliest cultivators of mathematical science. We are told, in fact, that they paved the way for Euclid and Archimedes, notwithstanding their symbolical and mystical fancies, and from their mathematical studies they were led to give exclusive supremacy to arithmetical and geometrical views of Nature. But what is curious about this whole speculation is, that in the invention or substitution of certain facts in order to make a perfect theory, it resembles some modern hypotheses, in which facts have been assumed, or argued as existing from analogies, when there is no evidence which establishes them. Modern instances of this will appear hereafter.

Enough has now been said about the speculations of the "early Greeks" to show the extravagance of Lord Macaulay's assertion that the discoveries of modern astronomy have placed the modern philosopher in no better situation to make safe deductions in natural theology than that occupied by the Hellenic philosophers from Thales to Plato. The evidences of design in the formation of the solar system—of that kind of design which acts in direct and specific exertions of a formative will—have been enormously multiplied by the discoveries of modern astronomy. Those discoveries, instead of leaving us to grope among theories which require the invention or imagination of facts, relate to facts that are demonstrated; and they tend in the strongest manner to establish the hypothesis of an infinite Creator, making laws to govern material objects, and then creating a system of objects to be governed by those laws. In a future chapter I shall endeavor to show why this hypothesis in regard to the solar system is most conformable to the rules of rational belief.

Not to anticipate what will be said hereafter concerning the modern discoveries in anatomy and in comparative zoÖlogy, it is enough to say here that in the writings of the Greek philosophers, especially of Plato and Aristotle, we may discover what the Greeks knew or did not know, and may therefore compare their knowledge with what is now known. What was known about the human anatomy to the Greeks of Plato's time is probably pretty well reflected in his "TimÆus," the celebrated dissertation in which he developed his theory of the Kosmos; for, although Plato in that superb philosophical epic made use of the organs of the human body for ethical and theological purposes, and did not make a special study of matters of fact, it is not probable that in his mode of using them he so far departed from the received ideas of his time respecting the human anatomy that his treatise would have been regarded by his contemporaries as an absurdity. Indeed, Mr. Grote considered that Plato had that anatomical knowledge which an accomplished man of his time could hardly fail to acquire without special study.[8] Moreover, even Galen, who came five centuries after Plato, and whose anatomical knowledge was far greater than could have been commanded in Plato's day, was wholly wrong in respect to the functions of some of the human organs. He agreed with Plato's ethical view of the human organism, but not in his physiological postulates. He considered, according to Mr. Grote, that Plato had demonstrated the hypothesis of one soul to be absurd; he accepted Plato's triplicity of souls, but he located them differently. He held that there are three "originating and governing organs in the body: the brain, which is the origin of all the nerves, both of sensation and motion; the heart, the origin of the arteries; the liver, the sanguifacient organ, and the origin of the veins which distribute nourishment to all parts of the body. These three are respectively the organs of the rational, the energetic, and the appetitive soul."[9] Plato, on the other hand, had placed the rational soul in the cranium, the energetic soul in the thoracic cavity, and the appetitive soul in the abdominal cavity; he connected them by the line of the spinal marrow continuous with the brain, making the rational soul immortal, and the two inferior souls, or two divisions of one inferior soul, mortal. Galen did not decide what is the essence of the three souls, or whether they are immortal. Plato assigned to the liver a very curious function, or compound of functions, making it the assistant of the rational soul in maintaining its ascendency over the appetitive soul, and at the same time making it the seat of those prophetic warnings which the gods would sometimes vouchsafe to the appetitive soul, especially when the functions of the rational soul are suspended, as in sleep, disease, or ecstasy.

But while there was much scientific progress from Plato to Galen, and while Galen's physiological ideas of the functions of the brain, the heart, and the liver held their place until Harvey's discovery of the circulation of the blood in the seventeenth century, that discovery and the subsequent investigations proved that Galen, although not far wrong as to the brain, was wholly wrong as to the liver, and partially wrong as to the heart. Yet Galen's physiological theories concerning these organs were founded on many anatomical facts and results of experiments, such as could then be made.

There is another fact which marks the state of anatomical knowledge among the Greeks in the time of Plato, and of Aristotle, who belonged to the same century. The "TimÆus" of Plato shows that there were physicians at that period, and that he was acquainted with the writings of Hippocrates. The important fact is, as stated by Mr. Grote, that "the study and practice of medicine was at that time greatly affected by the current speculations respecting Nature as a whole; accomplished physicians combined both lines of study, implicating cosmical and biological theories."[10]

It is now only needful to say that modern anatomy and physiology afford aids to sound deductions in natural theology in reference to the structure of the human body as an animal organism, and all the functions of its different organs, which immeasurably transcend all that was known or assumed among the early Greeks, or in the time of Plato and Aristotle, or in the time of Galen. Notwithstanding the dispute whether the origin of man as an animal is to be referred to a special act of creation, or to the process of what has been called evolution, there can be no controversy on one point, namely, that modern anatomy and physiology have vastly increased our knowledge of the structure of the human frame, and the means of rational speculation upon the nature of intellect, as compared with any means that were possessed by the most accomplished and learned of the Greeks of antiquity. It matters little on which side of the controversy, between creation and evolution, the great anatomists of the present day range themselves. It is upon the facts which their investigations have revealed that we have to judge of the probable truth of the one hypothesis or the other. The probable destiny of man as an immortal being is an inquiry that has certainly lost nothing by our increased knowledge of the facts in his animal structure which tend to support the hypothesis of design in his creation.

Lord Macaulay attributes an utter failure to the efforts of the philosophers, from Plato to Franklin, to "prove" the immortality of the soul without the help of revelation. What did he mean by proof? Revelation is, of course, the only direct proof. It is so, because it is direct testimony of a fact, proceeding from the only source that can have direct and certain knowledge of that fact. When the evidences which are supposed to establish the existence and authority of the witness have become satisfactory to us, we are possessed of proof of our immortality, and this proof is the only direct evidence of which the fact admits, and it constitutes all that should be spoken of as proof. But there is collateral although inferior evidence—inferior, because it consists in facts which show a high degree of probability that the soul of man is immortal, although this kind of evidence is not like the direct testimony of a competent witness. Is all this presumptive evidence, with its weighty tendency to establish the probable truth of immortality, to be pronounced of no value, because it belongs to a different order of proof from that derived from the assertion of a competent witness to the fact? It is one of the advantages of our situation in this life, that the collateral evidence which tends to show the high probability of a future state of existence is not withheld from us. As a supplemental aid to the direct teaching of revelation, it is of inestimable importance if we do not obscure it by theories which pervert its force, and if we reason upon it on sound philosophical principles. What we have to do in estimating the probable truth of our immortality, as shown by the science of natural religion, is to give the same force to moral evidence in this particular department of belief, that we give to the moral evidence which convinces us of many things of which we have no direct proof, or of which the direct proof lies in evidence of another kind.

"He knew as much about it," said Voltaire, "as has been known in all ages—that is to say, very little indeed." This, like many of the witticisms of Voltaire, pressed into the service of an argument against the value of natural religion at the present day when studied by mature and disciplined minds, is quite out of place. What human reason has done in the course of three thousand years is not to be put on a par with the speculations of intelligent children or half-civilized men; and although some of the riddles which perplexed Eliphaz and Zophar have not had a perfectly satisfactory solution, it is quite wide from the truth to assert that there has been no approximation to a satisfactory solution, or that some of the riddles have not ceased to be the riddles which they were three thousand years ago. In that period there has been an accumulation of evidence concerning the phenomena of Nature, and the phenomena of mind, vast beyond comparison when placed in contrast with what was known in the tents of the Idumean emirs, and the importance of this accumulation of evidence is proved by the fact that theories have been built upon it which undertake to explain it by hypotheses that were never heard of before, and which may possibly leave the "riddles" in a far less satisfactory state than they were in the time of Job. On the other hand, while the companions of Job may have been unable to suggest to him any solution of the problems of life, it does not at all follow that we are as helpless as they were, even if we avail ourselves of nothing but what the science of natural theology can now teach us.[11]

It will be seen that I attach great importance to natural theology. But I do not propose to write for the confirmed believers in revelation, on the one hand, who have become convinced by the evidence which supports revelation; or for those, on the other hand, who believe nothing, and who have become confirmed in habits of thinking which unfit them for judging of the weight of evidence on such subjects as the existence of God and the creation of man. I write for that great mass of people of average intelligence, who do not understand accurately what the doctrine of evolution is as expounded by its leading representatives, and who do not know to what it leads. It will be found that in some respects there is a distinction between the school of which Darwin is the representative and the school which follows Spencer. To point out this distinction, and yet to show that both systems result in negatives which put an end to the idea of immortality, and that the weight of evidence is against both of them, is what I propose to do.