Silently and insensibly their experiences have been pressing men on towards the conclusion thus drawn. Not out of a conscious regard for these reasons, but from a habit of thought which these reasons formulate and justify, all minds have been advancing towards a belief in the constancy of surrounding coexistences and sequences. Familiarity with concrete uniformities has generated the abstract conception of uniformity—the idea of Law; and this idea has been in successive generations slowly gaining fixity and clearness. Especially has it been thus among those whose knowledge of natural phenomena is the most extensive—men of science. The mathematician, the physicist, the astronomer, the chemist, severally acquainted with the vast accumulations of uniformities established by their predecessors, and themselves daily adding new ones as well as verifying the old, acquire a far stronger faith in law than is ordinarily possessed. With them this faith, ceasing to be merely passive, becomes an active stimulus to inquiry. Wherever there exist phenomena of which the dependence is not yet ascertained, these most cultivated intellects, impelled by the conviction that here too there is some invariable connexion, proceed to observe, compare, and experiment; and when they discover the law to which the phenomena conform, as they eventually do, their general belief in the universality of law is further strengthened. So overwhelming is the evidence, and such the effect of this discipline, that to the advanced student of Nature, the proposition that there are lawless phenomena has become not only incredible but almost inconceivable.
This habitual recognition of law which already distinguishes modern thought from ancient thought, must spread among men at large. The fulfilment of fresh predictions that are made possible by every new step, and the further {159} command gained over Nature’s forces, prove to the uninitiated the validity of scientific generalizations and the doctrine they illustrate. Widening education is daily diffusing among the mass of men that knowledge of these generalizations which has been hitherto confined to the few. And as fast as this diffusion goes on, the belief of the scientific must become the belief of the world at large.
That law is universal, will become an irresistible conclusion when it is perceived that the progress in the discovery of laws itself conforms to law; and when this perception makes it clear why certain groups of phenomena have been reduced to law, while other groups are still unreduced. When it is seen that the order in which uniformities are recognized, must depend on the frequency and vividness with which they are repeated in conscious experience; when it is seen that, as a matter of fact, the most common, important, conspicuous, concrete, and simple, uniformities were the earliest recognized, because they were experienced oftenest and most distinctly; it will by implication be seen that long after the great mass of phenomena have been generalized, there must remain phenomena which, from their rareness, or unobtrusiveness, or seeming unimportance, or complexity, or abstractness, are still ungeneralized. Thus will be furnished a solution to a difficulty sometimes raised. When it is asked why the universality of law is not already fully established, there will be the answer that the directions in which it is not yet established are those in which its establishment must necessarily be latest. That state of things which is inferable beforehand, is just the state which we find to exist. If such coexistences and sequences as those of Biology and Sociology are not yet reduced to law, the presumption is, not that they are irreducible to law, but that their laws elude our present means of exploration. Having long ago proved uniformity throughout all the lower classes of relations, and having been step by step proving {160} uniformity throughout classes of relations successively higher and higher, if we have not yet succeeded with the highest classes, it may be fairly concluded that our powers are at fault, rather than that the uniformity does not exist. And unless we make the absurd assumption that the process of generalization, now going on with unexampled rapidity, has reached its limit, and will suddenly cease, we must infer that ultimately mankind will discover a constant order even among the most involved and obscure phenomena.
THE VALUATION OF EVIDENCE.
[First published in The Leader for June 25, 1853.]
With Spirit-rappings and Table-movings still the rage, and with the belief in Spontaneous Combustion still unextinguished, it seems desirable that something should be said in justification of that general scepticism with which the philosophical meet the alleged wonders that periodically turn the heads of the nation. Nothing less than a bulky octavo would be needed to contain all that might be written on the matter; and unfortunately such an octavo, when written, would be little read by those most requiring it. A brief hint or two, however, may find listeners among them.
“I tell you I saw it myself,” is the so-thought conclusive assertion with which many a controversy is abruptly ended. Commonly those who make this assertion think that after it nothing remains to be urged; and they are astonished at the unreasonableness of those who still withhold their belief. Though they reject many tales of witchcraft, many ghost stories whose marvels were attested by eye-witnesses—though they have repeatedly seen stage-conjurors seem to do things which they do not believe were really done—though they have heard of the Automaton Chess-player and the Invisible Girl, and have perhaps seen explanations of the modes in which the public were deluded by {162} them—though in all these cases they know that the facts were other than the spectators supposed them to be; yet they cannot imagine that their own perceptions have been vitiated by influences like those which vitiated the perceptions of others. Or, to put the thing more charitably and perhaps more truly, they forget that such vitiations are constantly occurring.
To observe correctly, though commonly thought very easy, every man of science knows to be difficult. Our faculties are liable to report falsely from two opposite causes—the presence of hypothesis, and the absence of hypothesis. To the dangers arising from one or other of these, every observation we make is exposed; and between the two it is hard to see any fact quite truly. A few illustrations of the extreme distortions arising from the one cause, and the extreme inaccuracy consequent on the other, will justify this seeming paradox.
Nearly every one is familiar with the myth prevalent on our sea-coasts, respecting the Barnacle Goose. The popular belief was, and indeed is still in some places, that the fruits on branches which hang into the sea become changed into shell-covered creatures called barnacles, found incrusting these submerged branches; and further, that these barnacles are in process of time transformed into the birds known as barnacle geese. This belief was not confined to the vulgar; it was received among naturalists. Nor was it with them simply an adopted rumour. It was based on observations which were recorded and approved by the highest scientific authorities, and published with their countenance. In a paper contained in the Philosophical Transactions, Sir Robert Moray says:—“In every shell that I opened . . . there appeared nothing wanting, as to the external parts, for making up a perfect sea-fowl; the little bill like that of a goose, the eyes marked, the head, neck, breast, wings, tail, and feet formed, the feathers everywhere perfectly shaped and blackish coloured, and the feet like those of other {163} waterfowl, to my best remembrance.” Now this myth respecting the barnacle goose has been exploded for some century and a half. To a modern zoologist who examines one of these cirrhipeds, as the barnacles are called, it seems scarcely credible that it could ever have been thought a chick; and what Sir Robert Moray could have taken for “head, neck, breast, wings, tail, feet, and feathers,” he cannot imagine. Under the influence of a pre-conception, here is a man of education describing as “a perfect sea-fowl” what is now known to be a modified crustacean—a creature belonging to a remote part of the animal kingdom.
A still more remarkable instance of perverted observation exists in an old book entitled Metamorphosis Naturalis, &c., published at Middleburgh in 1662. This work, in which is attempted for the first time a detailed account of insect-transformations, contains numerous illustrative plates, in which are represented the various stages of evolution—larva, pupa, and imago. Those who have any knowledge of Entomology will recollect that the chrysalises of all our common butterflies exhibit at the anterior end a number of pointed projections, producing an irregular outline. Have they ever observed in this outline a resemblance to a man’s face? For myself, I can say that though in early days I kept brood after brood of butterfly larvæ through all their changes, I never perceived any such likeness; nor can I see it now. Nevertheless, in the plates of this Metamorphosis Naturalis, each chrysalis has its projections so modified as to represent a burlesque human head—the respective species having different profiles given them. Whether the author was a believer in metempsychosis, and thought he saw in the chrysalis a disguised humanity; or whether, swayed by the false analogy which Butler makes so much of, between the change from chrysalis to butterfly and that from mortality to immortality, he considered the chrysalis as typical of man; does not appear. Here, however, is the fact, that influenced by some {164} pre-conception or other, he has made his drawings quite different from the actual forms. It is not that he simply thinks this resemblance exists—it is not that he merely says he can see it; but his preconception so possesses him as to swerve his pencil, and make him produce representations laughably unlike the realities.