MENTAL EVOLUTION AND NECESSARY TRUTHS. 357 

 MENTAL EYOLUTIOX AND NECESSAKY TKUTHS/ 



Br HEEBERT SPENCER. 



I AM not about to continue a controversy which I regret having 

 been provoked into by the misrepresentations of one who ignored 

 the contents of works he professed to review. Reply and rejoinder 

 may go on endlessly. I could not, to much purpose, argue with Mr. 

 Hayward, who, instead of taking such unconsciously-formed precon- 

 ceptions as those resulting from the infinite experiences of muscular 

 tensions and their effects, proposes to exemplify unconsciously-formed 

 preconceptions by a consciously-formed hypothesis concerning the re- 

 lation between weight and motion. Nor should I care to discuss any 

 question with my new anonymous assailant ; who, when certain ex- 

 amples given show the "exact quantitative relations" spoken of to 

 be those of direct proportion, describes me as "intensely unmathemat- 

 ical " because I subsequently use the more general expression as equiv- 

 alent to the more special — which, in the case in question, it is. 



The first of my objects in now writing is to remind " some by- 

 standers, who may from their antecedents be presumed competent to 

 judge," that the essential question is not a mathematical one, but a 

 logical and psychological one, in respect of which I am not aware that 

 senior wranglers, as such, can claim any special competence. Further, 

 even admitting the assumption that the question is mathematical, I 

 have to warn the reader that he will be much misled if he infers that 

 there are not "some by-standers who may from their antecedents be 

 presumed" more "competent to judge," who concur in the opinion 

 that tlie laws of motion cannot be demonstrated experimentally. 



My second object is to inclose, for publication in Nature^ a passage 

 now standing in type to be added to future impressions of " First Prin- 

 ciples" in farther elucidation of necessary truths, and our apprehen- 

 sions of them : 



" The consciousness of logical necessity is the consciousness that a 

 certain conclusion is implicitly contained in certain premises explicit- 

 ly stated. If, contrasting a young child and an adult, we see that this 

 consciousness of logical necessity, absent from the one, is present in 

 the other, we are taught that there is a growing up to the recoo-nition 



^ [The article published last month, to which we gave the title of " Punishing a Senior 

 Wrangler," was issued by Mr. Spencer in a pamphlet as a part of his " Replies to Criti- 

 cism." It led to a running fight in the columns of Nature^ which we have not printed. 

 A second "Senior Wrangler" having come to the rescue of the first, with assurances of 

 his "sympathy," and R. B. Hayward having pitched in, Mr. Spencer sends the above 

 communication to Nature^ which we reproduce, because of the permanent interest of 

 his argument. — Ed,] 



