b 9 2 THE POPULAR SCIENCE MONTHLY. 



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 other 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 con- 

 sent, not merely as a legitimate inference 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 manifested in the " molar " motion of masses, or con- 

 sisting in the " molecular " motion 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 fit, so nil fit ad nihilum. 1 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 at the time, and which have come to be 

 so in virtue of its whole previous culture. Who, for example, could 

 refuse to the marvellous aptitude for perceiving the relations of num- 

 bers, which displayed itself in the untutored boyhood of George Bid- 

 der and Zerah Colburn, the title of an intuitive gift ? But who, on the 

 other hand, can believe that a Bidder or a Colburn could suddenly 

 arise in a race of savages who cannot count beyond five ? Or, again, 

 in the history of the very earliest years of Mozart, who can fail to 

 recognize the dawn of that glorious genius, whose brilliant but brief 



months since, with reference to the attempt I had made to place " Common-Sense " upon 

 this basis {Contemporary Review, February, 18*72) : "When states 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 considei'able evidence that such acquired facilities of passing into 

 certain modes of cerebral action can in many cases be transmitted, more or less complete- 

 ly, 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 knowl- 

 edge of the subject qualifies me to have an opinion, I take much the same view of it that 

 you do, at least in principle." 



1 This is the form in which the doctrine now known as that of the " Conservation of 

 Energy " was enunciated by Dr. Mayer, in the very remarkable Essay published by him 

 in 1845, entitled "Die organische Bewegung in ihrem Zus ammenhange mit dem Stoff- 



