Ladies and Gentlemen—We live in and form a part of a system of things of immense diversity and perplexity which we call Nature, and it is a matter of the deepest interest to all of us that we should form just conceptions of the constitution of that system and of its past history. With relation to this Universe, man is in extent little more than a mathematical point, in duration but a fleeting shadow. He is arced shaken in the winds of force; but, as Pascal long ago remarked, although a reed, he is a thinking reed, and, in virtue of that wonderful capacity of thought, he has a power of framing to himself a symbolic conception of the Universe, which, although doubtless highly imperfect, and although wholly inadequate as a picture of that great Whole, yet is sufficient to serve him as a guide-book in his practical affairs. It has taken long, indeed, and accumulations of often fruitless labour, to enable man to look steadly at the glaring phantasmagoria of Nature, to notice her fluctuations, and what is regular among her apparent irregularities; and it is only comparatively lately, within the last few centuries, that t here has emerged the conception of a pervading order and a definite force of things, which we term the course of Nature.

But out of this contemplation of Nature, and out of man's thoughts concerning her, there has in these later times arisen that conception of the constancy of Nature to which I have referred, and that at length has become the guiding conception of modern thought. It has ceased to be almost conceivable to any person who has paid attention to modern thought, that chance should have any place in the Universe, or that events should follow anything but the not twat order of cause and effect. We have come to look upon the present as the child of the past and as the parent of the future; and as we have excluded chance from any share or part in the order of things, so in the present order of Nature men have come to neglect, even as a possibility, the notion of any interference with that order; and whatever may be men's speculative notions upon these points, it is quite certain t hat every intelligent person guides his life and risks his fortune upon the belief that the order of Nature is constant, and the relation of cause to effect unchanged.

The Question a Historical One.

In fact, there is no belief which we entertain which has so complete a logical basin as that to which I have just referred. It underlies tacitly every process of reasoning; it is the foundation of every act of the will. It is based upon the broadest induction, and h is verified by the most constant, regular, and universal of inductive processes. We must recollect that any human belief, however broad its basis, however defensible it may seem, is, after all, only a probable belief, and that our broadest generalizations are simply the highest degrees of probability. Though we page 7 are quite clear about the constancy of Nature at the present time, and in the present order of things, it by no means follows necessarily that we are justified in expanding this generalization into the past, and in denying absolutely that there may have been a time when evidence did not follow a first order, when the relations of cause and effect were not fixed and definite, and when external agencies did not intervene in the general course of Nature. Cautious men will admit that such a change in the order of Nature may have been possible, just as every candid thinker will admit that there may be a world in which two and two do not make four, and in which two straight lines do not in close a space. In fact this question with which I have to deal in the three lectures I shall have the honour of delivering before you, this question as to the past order of Nature, is essentially a historical question, and it is one that must be dealt with in the same way as any historical problem.

I will, if you please, in the first place, state to you what are the views which have been entertained respecting the order of Nature in the past, and then I will consider what evidence is in our possession bearing upon the question, and by what light of criticism that evidence is to be interpreted. So far as I know, there are only three views—three hypotheses—which ever have been entertained, or which well can be entertained, respecting the past history of Nature.

Hypothesis Respecting the Order of Nature.

Upon the first of these the assumption is that the order of Nature which now obtains has always obtained; in other words, that the present course of Nature, the present order of things, has existed from all eternity. The second hypothesis is that the present state of things, the present order of Nature, has had only a limited duration, and that at some period in the past the state of things which we now know—substantially, though not of course in all its details the state of things which we now know—arose and came into existence without any precedent similar condition from which it could have proceeded. The third hypothesis also assumes that the present order of Nature has had but a limited duration, but it supposes that the present order of things proceeded by a natural process from an antecedent order, and that from another antecedent order, and so on; and that on this hypothesis the attempt to fix any limit at which we could assign the commencement of this series of changes is given up. I am very anxious that you shall realize what these three hypotheses actually mean; that is to say, what they involve, if you can imagine a spectator to have been present during the period to which they refer. On the first hypothesis, however far back in time you place that spectator, he would have seen a world, essentially similar, though not perhaps in all its details, to that which now exists. The animals which existed would be the ancestors of those which now exist, and like them; the plants in like manner would be such as we have now, and like them; and the supposition is that at however distant a period of time you place your observer, he would still find mountains, lands, and waters, with animal and vegetable products flourishing upon them and sporting in them just as he finds now. That view has been held. It was a favourite fancy of antiquity, and has survived along down towards the present day, and it is worthy of remark that it is a hypothesis which is not inconsistent with what geologists are familiar with as the doctrine of Uniformitarianism. That doctrine was held by Hutton, and in his earlier days by Lyell. For Hutton was struck by the demonstration of astronomers that the perturbations of the planetary bodies, however great they may be, yet sooner or later righted themselves, and that the solar system contained within itself a self-adjusting power by which these aberrations were cured and it brought back to an equilibrium

Hutton imagined that something of the same kind may go on in the earth, although no one recognised more clearly than he the fact that the dry land is being constantly washed down by rain and rivers and deposited in the sea, and that thus in a certain length of time, greater or shorter, the inequalities of the earth's surface must be levelled and its high lands brought down to the sea. Then, taking in account the internal forces of Nature, by which upheavals become seated and give page 8 rise to new land, these operations may naturally compensate each other, and thus substantially for any assignable time the general features of the earth might remain what they are. And inasmuch as there is no limit under these circumstances to the successive development of the animals and plants, it is clear that the logical development of this idea might lead to the conception of the eternity of the world. Not that I mean to say that either Hutton or Lyell held this conception—assuredly not; they would have been the first to repudiate it. But by the arguments they used it might have been possible to justify this hypothesis.

The Theory of Creation in Paradise Lost.

The second hypothesis is that to which I have referred as the hypothesis which supposes that this order of things had at some no very remote time a sudden origin making it such as it now is. That is the doctrine which you will find stated most fully and clearly in the immortal poem of John Milton, the English Divina Commedia, "Paradise Lost." I believe it is alone through the influence of that remarkable work, combined with daily teachings to which we have all listened in our childhood, that this hypothesis owes its general wide diffusion as one of the current beliefs of English-speaking people. If you turn to the VIIth book of "Paradise Lost," you will find there stated the theory, the hypothesis to which I refer, which is this: That this visible Universe of ours made its appearance at no great distance of time from the present day, and that the parts of which it is composed made their appearance in a certain definite order in the space of six natural days, in such a manner that in the first of these days light appeared; in the second, the firmament or sky separated the water above from the water beneath it; on the third day the waters drew away from the dry land, and from it the vast vegetable life which now exists made its appearance; that the fourth day was devoted to the apparition of the sun, the stars, the moon, and the planets; that on the fifth day aquatic animals originated within the waters; and then on the sixth day the earth gave rise to our four-footed terrestrial creatures and to all varieties of terrestrial animals except birds, which had appeared on the preceding day; and finally, man appeared upon the earth, and the work of fashioning the Universe was finished. John Milton, as I have said, leaves no doubt whatever as to how, in his judgment, these marvellous processes occurred. I doubt not that his immortal poem is familiar to all of you, but I should like to recall one passage to your minds, in order that I may be justified in what I shall have to say. Regarding the perfectly concrete, definite conception which Milton had of what he thought had been the mode of origin of the animal world, he says:—

The sixth, and of creation last, arose
With evening harps and matin; when God said,
"Let the Earth bring forth soul living in her kind,
Cattle and creeping things, and beast of the earth,
Each in their kind." The earth obey'd, and straight
Opening her fertile womb, teem'd at a birth
Innumerous living creatures, perfect forms,
Undid and full-grown; out of the ground up rose
As from his lair, the wild beast, where he wons
In forest wild, in thicket, brake, or den;
Among the trees in pairs they rose, and walk'd;
The cattle in the fields and meadows green;
Those rare and solitary, these in flocks
Pasturing at once, and in broad herds upsprung.
The grassy clods now calved; now half appears
The tawny lion, pawing to get free
His hinder parts, then springs, as broke from bonds,
And rampant shakes his blinded mane; the ounce,
The libber!, and the tiger, as the mole
Rising, the crumbled earth above them threw
In hillocks; the swift stag from under ground
Bore up his branching head; scarce from his mould
Behemoth, biggest born of earth, upheav'd
His vastness; fleeced the flocks and bleating rose
As plants; ambiguous between sea and land,
The river-horse and scaly crocodile
At once canto forth whatever creeps the ground
Insect or worm.

There is no doubt as to the meaning of that hypothesis, or as to what a man of Milton's genius expected would have been actually visible to one who could know and witness the process, the origination of living things as he describes it.

The Evolution Hypothesis.

And then comes the third hypothesis, which is the hypothesis of Evolution, and that supposes that at any given period in the past we should meet with a state of things more or less similar to the present, but less similar in proportion as we go back in time; that the physical form of the earth could be traced back in this way to a condition in which its parts were separated, as little more than & nebulous cloud making part of a whole in which we find the sun and the other planetary bodies also resolved; and that if we traced back the animal world and the vegetable world, we should find preceding what now exist animals and plants not identical with them, but like them, only increasing their differences as we go back in time, and at the same time becoming simpler and simpler, until finally we should arrive at that gelatinous mass which, so far as our present knowledge goes, is the common foundation of all life. The tendency of science is to justify the speculation that that also could be traced further back, perhaps to the general nebulous origin of matter.

The hypothesis of Evolution supposes that in all this vast progression there would be no breach of continuity, no point at which we could say "this is a natural process," and "this is not a natural process," but that the whole might be strictly compared to that wonderful series of changes which may be seen going on every day under our eye, in virtue of which there arises out of that semi-fluid, homogeneous substance which we call an egg, the complicated organisation of one of the higher animals. That, in a few words, is what is meant by the hypothesis of Evolution.

I have already suggested that in dealing with these three hypotheses, endeavouring to form a judgment as to which of them is the more worthy of belief, or whether none is worthy of belief, our condition of mind should be that suspension of judgment which is so difficult to all but trained minds—I have suggested that in dealing with these questions we should be indifferent to all a priori considerations. The question is a question of fact, historical fact. The Universe has come into existence somehow or other, and the question is whether it came into existence in one fashion, or whether it came into existence in another; and as the essential preliminary to this consideration, permit me to say two or three words as to the nature of' historical evidence, and the kinds of historical evidence. The evidence as to the occurrence of any fact in past time is of one or two kinds, which for convenience sake, I will speak of on the one hand as testimonial evidence, and on the other as circumstantial evidence. By testimonial evidence, I mean human testimony; and by circumstantial evidence, I mean evidence which is not human testimony. Let me illustrate by a familiar figure what I mean by these two kinds of evidence, and what is to be said respecting their value.

Human and Circumstantial Testimony Compared.

Suppose that a man tells you that he saw a person strike another and kill him; that is testimonial evidence of the fact of murder. But it is possible to have circumstantial evidence of the fact of murder. That is to say, you may find a man dying with a wound upon his head having exactly the form and character of the wound which is made by an axe, and with due precaution you may conclude with the utmost certainty that the man has been murdered—is dying in consequence of the violence inflicted by that implement. We are very much in the habit of considering circumstantial evidence as of less value than testimonial evidence, and it may be in many eases where the circumstances are not perfectly clear and perfectly intelligible that it is a dangerous and uncertain kind of evidence; but it must not be forgotten that in many cases it is quite as good as testimonial evidence, and that in many eases it is a great deal better than testimonial evidence. For example, take the case to which I referred just now. The circumstantial evidence is better and more convincing than the testimonial evidence, foe it is impossible under the circumstances that I have mentioned to suppose that page 10 the man had met his death from any cause but the violent blow of the axe. The circumstantial evidence in favour of a murder having been committed, in that case is as complete and as convincing as evidence can be. It is evidence which is open multitudinous doubts. He may have been actuated by malice. It has constantly happened that even an accurate man has declared a thing has happened in some particular way, when a careful analysis of the circumstantial evidence has shown that it did not happen in that way, but in some other way.

Now we must turn to our three hypotheses. Let me first direct your attention to what is to be said about the hypothesis of the eternity of this state of thins in which we now are. What will first strike you is that that is a hypothesis which, whether true or false, is not capable of verification by evidence; for in order to secure testimony to an eternity of duration you must have a eternity of witnesses or an infinity of circumstances, and neither of these are attainable, It is utterly impossible that such evidence should be carried beyond a certain point of time, and all that could be said at most would be that there was nothing to contradict the hypothesis. But when you look, not to the testimonial evidence—which might not be good for much in this case—but to the circumstantial evidence, then you find that this hypothesis is absolutely incompatible with that circumstantial evidence, and the latter is of so plain and so simple a character that it is impossible in any way to escape from the conclusions which it forces upon us.