3 6 THE POPULAR SCIENCE MONTHLY. 



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 differ- 

 ent 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, par- 

 don 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 opera- 

 tion, 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 condi- 

 tions 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 sugges- 

 tions which may be made for the improvement of natural arrange- 

 ments. 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 lan- 

 guage, it may be described as asserting that the motion of bodies gen- 

 erally 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 sys- 

 tem may be solved. The remarkable fact connected with this prin- 

 ciple is, that its truth was evolved by a speculative mind out of the 

 general principle that nature would use the least effort possible to pro- 

 duce a given result, before it was demonstrated in its strict form by 





