160. 103 



850.1 



II 



Scientific Proofs versus ' A Priori ' Assumptions 



UNTIL the great impetus had been given by Darwin to the 

 acceptance of the Doctrine of Evolution, by the publication 

 of his " Origin of Species," natural science mainly consisted of the 

 observation of facts. Thus, old text-books of botany contained the 

 names and descriptions of the various organs of plants with little 

 or no attempt to deal with their physiological uses, much less with 

 their origins. The old idea, that ' species ' were fixed entities, 

 created as we now see them, with all their organs complete, led 

 men tacitly to assume that such descriptions were all that was 

 necessary. Botany mostly consisted of the accumulation of morpho- 

 logical facts to aid the systematise If any suggestions were pro- 

 posed as to the purpose of this or that organ, the use of which was 

 not very obvious, ' teleological guesses,' as they might be called, were 

 thought to be amply sufficient to account for them. The Bridge- 

 water treatises may be taken as the type of that old method of 

 interpretation of 'uses,' which was, in fact, simply that of it priori 

 assumptions without any strictly scientific bases to go upon; by 

 which I mean neither any accurate observations nor experiments, 

 wherewith to verify the supposed uses. 



Like that of teleology, it has now come to be generally recog- 

 nised that the inherent fallacy underlying metaphysics is due to the 

 want of external observations and experimental proofs ; so that no 

 worker in natural science can well be a metaphysician at the same 

 time, for the methods of proof — if any such term can be applicable 

 to metaphysics at all— lie in opposite directions. The scientific 

 student should be satisfied only with objective facts ; the meta- 

 physician is contented with subjective imaginations. 



Darwin published "The Origin of Species" in 1859. This 

 work at once broke down the old ideas of the fixity of species, 

 as having been created such, and having unalterable forms ; but 

 the question immediately arose : How are new forms worked out by 

 evolution in nature ? 



Darwin and Dr Wallace simultaneously propounded the theory 

 of Natural Selection. Though differing in some important points, 

 both based their conclusions on the following statements : — 



(1) That more offspring are born than can ever live to maturity 

 and so leave fresh offspring. 



( 2 ) That no two individuals of the same kind are ever abso- 



