These remarks are addressed to an Association for the advancement of science—of science which flourishes and progresses by the aid of suppositions and the working of the imagination. The Association has been holding its annual sitting in various parts of the British Islands for more than thirty years, and yet it is still a very common and widely spread notion that science, that is to say, true science according to those who hold the notion, does not countenance hypotheses, and sternly occupies itself with the exact record of fact. On the other hand, there are many persons who run to an opposite extreme, and call by the name of science any fanciful attempt to deal with or account for a certain class of phenomena. The words “science” and “scientific” are used so vaguely and variously that one might almost come to the conclusion that it would be well for our Association to plainly state what is that thing for the advancement of which its meetings are held. I cannot venture to speak in the name of my colleagues; and no doubt a review of the work done by the Association would most fitly explain what that body understands by the word “science.” At the same time it is permissible to take this opportunity of briefly stating what science is and what it is not, so far as I am able to judge of the fitting use of the word.
Science is certainly not any and every kind of knowledge. Knowledge of literature, of the beautiful things which have been written or otherwise produced by human ingenuity, is not science. Knowledge of the various manufacturing processes in use by civilised men is not science; nor knowledge of the names of the stars, or of the joints of a beetle’s leg. Science cannot be identified with knowledge of any particular class of objects, however detailed that knowledge may be. It is a common mistake to consider all knowledge of raw products, of living objects or other natural objects, as necessarily “science.” The truth is, that a man may have great knowledge of these things as so many facts, and yet be devoid of “science.” And, on the other hand, that which is properly called science embraces not only such subject-matter as that just alluded to, but also may find its scope in the study of language, of human history, and of the workings of the human mind.
The most frequent and objectionable misuse of the word ‘science’ is that which consists in confounding science with invention—in applying the term which should be reserved for a particular kind of knowledge to the practical applications of that knowledge. Such things as electric lighting and telegraphs, the steam-engine, gas, and the smoky chimneys of factories, are by a certain school of public teachers, foremost among whom is the late Oxford Professor of Fine Art, persistently ascribed to science, and gravely pointed out as the pestilential products of a scientific spirit. They are, in fact, nothing of the kind. American inventors and electric lamps, together with all the factories in Sheffield, might be obliterated without causing a moment’s concern to a single student of science. It is of the utmost importance for the progress and well-being of science that this should be understood; that the eager practical spirit of the inventor who gains large pecuniary rewards by the sale of his inventions should not be confounded with what is totally different and remote from it, namely, the devoted, searching spirit of science, which, heedless of pecuniary rewards, ever faces nature with a single purpose—to ascertain the causes of things. It seems to me impossible to emphasise too strongly in such a place and in such a meeting as this, that Invention is widely separate from, though dependent on, Science. Invention is worldly-wise, and despises the pursuit of knowledge for its own sake. She awaits the discoveries of Science, in order to sell them to civilisation, gathering the golden fruit which she has neither planted nor tended. Invention follows, it is true, the footsteps of Science, but at a distance: she is utterly devoid of that thriftless yearning after knowledge, that passionate desire to know the truth, which causes the unceasing advance of her guide and benefactress.
We may, it seems to me, say that of all kinds and varieties of knowledge that only is entitled to the name “science” which can be described as Knowledge of Causes, or Knowledge of the Order of Nature. It is this knowledge to which the great founder of European science—Aristotle the Greek—pointed as true knowledge: τότε ἐπιστάμεθα ὅταν τὴν αἰτίαν εἴδωμεν. Science is that knowledge which enables us to demonstrate so far as our limited faculties permit, that the appearances which we recognise in the world around us are dependent in definite ways on certain properties of matter: science is that knowledge which enables, or tends to enable us, to assign its true place in the series of events constituting the universe, to any and every thing which we can perceive.
The method by which scientific knowledge is gained—knowledge of the causes of nature—is precisely the same as that by which knowledge of causes in every-day life is gained. Something—an appearance—has to be accounted for: the question in both cases is “Through what cause, in relation to what antecedent is this appearance brought about?” In scientific inquiry, as in every-day life, a hypothesis—a provisional answer or guess—is the reply; and the truth of that guess or hypothesis is then tested. This testing is an essential part of the process. “If my guess be true, then so-and-so as to which I can decide by inspection or experiment, must be true also,” is the form which the argument takes, and the inquiry is thus brought to a point where observation can decide the truth of the hypothesis or first guess. In every-day life we have often to be content without fully testing the truth of our guesses, and hurry into action based on such unverified suppositions. Science, on the other hand, can always wait, and demands again and again the testing and verification of guesses before they are admitted as established truths fit to be used in the testing of new guesses and the building up of scientific doctrine.
The delicately-reared imaginations of great investigators of natural things have from time to time given birth to hypotheses—guesses at truth—which have suddenly transformed a whole department of knowledge, and made the causes of things quite clear which before seemed likely to remain always concealed. So great is the value of hypothesis, so essential to scientific discovery, that the most skilled and highly-trained observer may spend his life in examining and scrutinising natural objects and yet fail, if he is not guided by hypothesis, to observe particular facts which are of the uttermost importance for the explanation of the causes of the things which he is studying. Nature, it has been said, gives no reply to a general inquiry—she must be interrogated by questions which already contain the answer she is to give; in other words, the observer can only observe that which he is led by hypothesis to look for: the experimenter can only obtain the result which his experiment is designed to obtain.
For a long time the knowledge of living things, of plants and of animals could hardly be said to form part of the general body of science, for the causes of these things were quite unknown. They were kept apart as a separate region of nature, and were supposed to have been pitched, as it were, into the midst of an orderly and cause-abiding world without cause or order: they were strangers to the universal harmony prevailing around them. Fact upon fact was observed and recorded by students of plants and animals, but having no hypothesis as to the causes of what they were studying, the naturalists of twenty years ago, and before that day, though they collected facts, made slow progress and some strange blunders. Suddenly one of those great guesses which occasionally appear in the history of science, was given to the science of biology by the imaginative insight of that greatest of living naturalists—I would say that greatest of living men—Charles Darwin.
In the form in which Mr. Darwin presented his view to the world it was no longer a mere guess. He had already tried it and proved it in an immense series of observations; it had already been converted by twenty years’ labour on his part into an established doctrine, and the twenty years which have passed since he published the Origin of Species have only served to confirm, by thousands of additional tests, the truth of his original guess.
Space will not allow me to go fully into the history of the Darwinian theory, but it is necessary for my present purpose that I should state precisely what that theory is. It involves a number of subordinate hypotheses which, together with the main hypothesis, furnish us with a complete “explanation,” as it is called, of the facts which have been ascertained as to living things; in other words, it assigns living things to their causes, gives them their place in the Order of Nature.
It is a very general popular belief at the present day that the Darwinian theory is simply no more than a capricious and anti-theological assertion that mankind are the modified descendants of ape-like ancestors.