Page:Popular Science Monthly Volume 17.djvu/46

 its own peculiar difficulties and its own anomalies and contradictions. A really complete scientific theism, such a theism as Bacon would have delighted to map out in detail, would comprehend all the different departments of which I have spoken, and in the unity of such a system physicists and philosophers and divines would be able to meet and shake hands.

It is a curious subject of inquiry, and the reader will, I think, pardon me for here introducing it, how far, upon the theistic view of nature, we can discriminate between that which is necessary in the nature of things and that which is to be regarded as being such as it is in virtue of a divine purpose or choice. It seems clear, for example, that when once matter is assumed to be the subject of a divine operation, as in the case of the universe with which we are acquainted and of which we form a part, certain necessary conditions are imposed upon the creative work or upon the system of nature. These conditions may be, in a certain sense, limitations of divine power; but they are not limitations in any more objectionable sense than are the truths of geometry or number, to which all created things must be conformable. Sometimes a condition of this kind exists which is not at all obvious at first sight, and which, nevertheless, is as necessary to be taken into account as the truth that two and two make four and can not make five. Thus, for example, Laplace suggests that the utility of the moon is not as great as it might have been, and he points out an arrangement according to which, as he shows, the earth would have received much more light than it actually does; but I remember having read a memoir by Liouville in one of the numbers of his "Journal," in which he shows that the arrangement proposed by Laplace would not be stable—that is, that it would only be possible in the sense in which it is possible to make a pin stand upon its point. An example of this kind shows the necessity of caution in any suggestions which may be made for the improvement of natural arrangements. But it does more than this; it helps to illustrate the point which I am now endeavoring to discuss, with reference rather to the philosophy of the arrangements which we see than to any suggestions for improving them.

Let us consider for a moment what is called by mathematicians the principle of least action. Putting this principle into popular language, it may be described as asserting that the motion of bodies generally takes place in such a manner that the energy expended in the motion is the least possible. From this principle, when enunciated in a strict mathematical form, the equations of motion of a system may be deduced, or, in other words, the problem of the motion of a system may be solved. The remarkable fact connected with this principle is, that its truth was evolved by a speculative mind out of the general principle that nature would use the least effort possible to produce a given result, before it was demonstrated in its strict form by