Page:Mind (Old Series) Volume 11.djvu/566

 THE DEFINITION OF NATURAL LAW. 565- tends to make us regard a natural law, not as a uniformity of process under certain circumstames, but as a uniformity of process n/iiliT all circumstances. The result of this misconception is obvious. The moment we lose sight of the limited and relative character of all human observation, and begin to regard natural laws as invariable, not only under previously ascertained conditions, but under all con- ditions whatever, we transcend the limits of legitimate inference, and practically shut up progress in a cul-de-sac. I do not waver a hair's breadth from my faith in the absolute jurisdiction of Natural Law in its widest sense ; I only demur to the fallacious assumption that " natural law " must be treated as equivalent to " ascertained natural law " only ; in other words, to the assumption that the possibilities of things can be logically limited to the ascertained possibilities of experience. Experience is a sure guide so far as it goes, but nobody will pretend that the experience of the world to-day has exhausted all the possibilities of the experience of the future. With regard to what I may call purely physical laws of nature, the ascertainment-clause is less likely to lead to serious error. But why ? Simply because the conditions under which the commoner physical laws operate are, for practical purposes, already ascertained. We can pronounce with absolute confidence upon the phenomena of gravitation as shown by material bodies, because, from their comparative simplicity and the frequency of their occurrence, we are intimately acquainted with their neces- sary conditions. But the moment we turn from these to the phenomena of life and mind, we must needs leave our certainty behind us. Nor is this in any way a matter for surprise. Both the science of life and the science of mind are yet in their infancy; and, even apart from this, their phenomena display an intricate complexity in place of the comparative simplicity of the pheno- mena of physical laws. This difference appears on the very threshold, as the distinction between organic and inorganic chemistry sufficiently shows. We are doubtless entitled to attach as much weight to ascertained uniformities in the biological or the psychological branch of science as we allow to the ascertained uniformities of physical law. But in these comparatively un- explored spheres of inquiry we are not entitled to deny that an occurrence is possible, because it has not fallen within previous observation. Let me not be misunderstood. I do not impeach in the slightest degree the validity of ascertained biological or psychological laws. Such laws must be loyally admitted so far as they go. I only contend that they do not necessarily go far enough. They may be true accounts of certain biological or psychological facts, but they do not exclude the possibility of other and apparently conflicting biological or psychological facts. Let me take a prominent instance in biology to illustrate this. The doctrine of ' Biogenesis ' is probably accepted by ninety per