198 NATURE AND MAN. 



We have an illustration of this progress in the fact of continual 

 occurrence, that conceptions which prove inadmissible to the 

 minds of one generation, in consequence either of their want of 

 intellectual power to apprehend them, or of their preoccupation by 

 older habits of thought, subsequently find a universal acceptance, 

 and even come to be approved as " self-evident." Thus the first 

 law of motion, divined by the genius of Newton, though opposed 

 by many philosophers of his time as contrary to all experience, is 

 now accepted by common consent, not merely as a legitimate in- 

 ference from experiment, but as the expression of a necessary and 

 universal truth ; and the same axiomatic value is extended to the 

 still more general doctrine, that energy of any kind, whether mani- 

 fested in the " molar " motion of masses, or consisting in the 

 "molecular" motions of atoms, must continue under some form 

 or other without abatement or decay ; what all admit in regard to 

 the indestructibility of matter, being accepted as no less true of 

 force, namely, that as ex nihilo nil jit, so nil fit ad 7iihilum* 



But, it may be urged, the very conception of these and similar 

 great truths is in itself a typical example of intuition. The men 

 who divined and enunciated them stand out above their fellows, 

 as possessed of a genius which could not only combine but create, 

 of an insight which could clearly discern what reason could but 

 dimly shadow forth. Granting this freely, I think it may be shown 

 that the intuitions of individual genius are but specially exalted 

 forms of endowments which are the general property of the race 



"common sense" upon this basis (Coufciaf'orary Revi-ew, February, 1S72) : — 

 " When st.ites of mind in no respect innate or instinctive have been frequently 

 " repeated, the mind acquires, as is proved by the power of habit, a greatly 

 • increased facility of passing into those states ; and this increased facility must 

 "be owing to some change of a physical character in the organic action of the 

 "brain. There is also considerable evidence that such acquired facilities of 

 "passing into certain modes of cerebral action can, in many cases, be trans- 

 "mitted, more or less completely, by inheritance. The limits of this power 

 "of transmission, and the conditions on which it depends, are a subject now 

 " fairly before the scientific world ; and we shall doubtless in time know much 

 "more about them than we do now. But so far as my imperfect knowledge 

 "of the subject qualifies me to have an opinion, I take much the same view of 

 "it that you do, at least in principle." 



* This is the form in which the doctrine now known as that of the "Con- 

 servation of Energy " was enunciated by Dr. Mayer, in the very remarkable 

 essay published by him in 1S45, entitled, " Die organische Eewegung in ihrem 

 Zusainmenhange mit dem Stolfwechsel." 



