“It has taken long indeed, and accumulations of often fruitless labor, to enable men to look steadily 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 there has emerged the conception of a pervading order and definite force of things, which we term the course of nature. But out of this contemplation of nature, and out of man’s thought 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 natural order of cause and effect.”
The truth is that “modern thought” has had no part whatever in the discovery of the constancy of nature. This discovery is as old as mankind. All ancient philosophers, even before Aristotle, knew the constancy of the natural laws, and this knowledge has never died away, that modern thinkers should claim the honor of reviving it. The same is to be said of “the conception of a pervading order and definite force of things,” as we find that old Greek and Latin books are full of this conception, which is likewise common to all our mediæval writers, and, indeed, to all reasonable men. That “chance” could have no place in the universe was so well known to the ancients that Cicero emphatically declared any
man to be silly who would suspect the possibility of the contrary.[152] Hence no person ever needed “to pay attention to modern thought” to conceive that chance could have no place in the government of the world. Finally, that events cannot but follow “the natural order of cause and effect” is the oldest of scientific truths, and the first principle of scientific reasoning. A lecturer who pretends that we owe these truths to “modern thought” shows no respect for his audience. On the other hand, if “modern thought” is so poor and barren that it envies the scientific claims of past generations, and stakes its reputation on fiction and plagiarism, what can we say of the wisdom of the modern thinker who affords a ground for arguing that “modern thought” stands convicted of dishonesty as much as of incapacity?
The professor a little later says:
“Though we 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 enclose a space.”
This sentence shows that we are dealing rather with an empiricist than with a natural philosopher. Why should not the constancy of
nature at the present time justify our conviction that nature has been no less constant in the past? Surely, if we proceed only empirically, the facts of the present will teach us nothing certain as to the facts of a remote and unknown past. But it is remarkable that this purely empirical method would leave us equally uncertain as to the facts of the future, though modern scientists assure us that “the future must be similar to the past.” The truth is that no valid induction can be made from mere facts without the aid of a rational principle as the ground of our generalization. If such a principle is certain, our inference is certain; and if the principle is only plausible, our inference will be plausible in the same degree. Now, have we not a certain principle from which the constancy of nature can be demonstrated with no reference to particular time? We have such a principle. We infer the constancy of nature from the constancy of the agencies by which the physical order is ruled. All elementary substances are permanent; their matter and their active power are never impaired; the law of their activity is as fixed and definite as their permanent constitution; and therefore they do not, and they cannot, act at present in a different manner from that in which they have acted from the beginning, or from that in which they will act as long as they last. This is the principle by which we are fully justified in extending the constancy of nature to all antiquity and to all futurity, and in averring that such a constancy is not an accidental result of circumstances, but a necessary consequence of the principle of causality.
But Mr. Huxley seems not to understand this principle. He imagines
a time when the relations of cause and effect may not have been fixed and definite, and even conceives the possibility of a world in which two and two do not make four. This is modern thought indeed; for we do not believe that any indication can be found of a similar thought having ever been entertained in past ages. But we would ask: If in a certain world two and two did not make four, how could Mr. Huxley know that they make four in this world? And if the relations of cause and effect had at any given time remained vague and indefinite, how could he account for the fact that they are now definite and fixed? For the relation of cause and effect consists in this: that the impression produced by the cause is the exact equivalent of the exertion made in its production; and he who imagines a time when such a relation was not fixed and definite must assume that an effect can be greater than the exertion in which it originates, or that the exertion can be greater than the impression it produces. But if so, on what ground can the professor affirm that the relation of cause and effect has now become fixed and definite? We see the effect, but we cannot see the exertion; we see the fall of a body, but we cannot see the action of gravity. How, then, can Mr. Huxley ascertain that the action of gravity is neither greater nor less than the momentum impressed on the body? Thus the relation of cause and effect, in his theory, cannot be known; and mechanical science becomes impossible. In the same manner, if, in another world, two and two do not make four, mathematics are an imposition.
The lecturer says also that there may have been a time “when external