32S 



INDUCTION. 



exist." * But the hypothesis would 

 have been false, though no such direct 

 evidence of its falsity had been pro- 

 curable. Direct evidence of its truth 

 there could not be. 



The prevailing hypothesis of a lu- 

 miniferous ether, in other respects not 

 without analogy to that of Descartes, 

 is not in its own" nature entirely cut 

 off from the possibility of direct evi- 

 dence in its favour. It is well known 

 that the difference between the cal- 

 culated and the observed times of the 

 periodical return of Encke's comet, 

 has led to a conjecture that a medium 

 capable of opposing resistance to mo- 

 tion is diffused through space. If 

 this surmise should be confirmed, in 



an operation which could only be tentative, 

 though we may regret that materials barely 

 sufficient for a first rvide hypothesis should 

 have been hastily worked up into the vain 

 semblance of a science. If there be really 

 a connection between the scale of mental 

 endowments and the various degrees of 

 complication in the cerebral system, the 

 nature of that connection was in no other 

 way so likely to be brought to light as by 

 framing, in the first instance, an hypo- 

 thesis similar to that of Gall. But the 

 verification of any such hypothesis is at- 

 tended, from the peculiar nature of the 

 J)henomena, with difficulties which phreno- 

 ogists have not shown themselves even 

 competent to appreciate, much less to 

 overcome. 



Mr. Darwin's remarkable speculation on 

 the Origin of Species is another unimpeach- 

 able example of a legitimate hypothesis. 

 What he terms "natural selection" is not 

 only a vera causa, but one proved to be 

 capable of producing effects of the same 

 kind with those which the hypothesis 

 ascribes to it : the question of possibility 

 is entirely one of degree. It is unreason- 

 able to accuse Mr. Darwin (as has been 

 done) of violating the rules of Induction. 

 The rules of Induction are concerned with 

 the conditions of Proof. Mr. Darwin has 

 never pretended that his doctrine was 

 proved. He was not bound by the rules 

 of Induction, but by those of Hypothesis. 

 And these last have seldom been more 

 completely fulfilled. He has opened a 

 path of inquiry full of promise, the results 

 of which none can foresee. And is it not 

 a wonderful feat of scientific knowledge 

 and ingenuity to have rendered so bold a 

 suggestion, which the first impulse of every 

 one was to reject at once, admissible and 

 discussable, even as a conjecture? 



* Whttwell'a Phil, of Ditcovery, pp. 275, 

 276. 



the course of ages, by the gradual 

 accumulation of a similar variance in 

 the case of the other bodies of the 

 solar system, the luminiferous ether 

 would have made a considerable ad- 

 vance towards the character of a vera 

 can^a, since the existence would have 

 been ascertained of a great cosmicai 

 agent, possessing some of the attri- 

 butes which the hypothesis assumes 1 

 though there would still remain manj 

 difficulties, and the identification of 

 the ether with the resisting medium 

 would even, I imagine, give rise to 

 new ones. At present, however, this 

 supposition cannot be looked upon as 

 more than a conjecture ; the exist- 

 ence of the ether still rests on the 

 possibility of deducing from its as- 

 sumed laws a considerable number of 

 actual phenomena ; and this evidence 

 I cannot regard as conclusive, be- 

 cause we cannot have, in the case 

 of such an hypothesis, the assurance 

 that if the hypothesis be false it must 

 lead to results at variance with the 

 true facts. 



Accordingly, most thinkers of any 

 degree of sobriety allow, that an 

 hypothesis of this kind is not to be 

 received as probably true because it 

 accounts for all the known pheno- 

 mena, since this is a condition some- 

 times fulfilled tolerably well by two 

 conflicting hypotheses ; while there 

 are probably many others which are 

 equally possible, but which, for want 

 of anything analogous in our expe- 

 rience, our minds are unfitted to con- 

 ceive. But it seems to be thought 

 that an hypothesis of the sort in ques- 

 tion is entitled to a more favourable 

 reception, if, besides accotinting for 

 all the facts previously known, it has 

 led to the anticipation and prediction 

 of others which experience afterwards 

 verified ; as the undulatory theory of 

 light led to the prediction, subse- 

 quently realised by experiment, that 

 two luminous rays might meet each 

 other in such a manner as to produce 

 darkness. Such predictions and their 

 fulfilment are, indeed, well calculated 

 to impress the uninformed, whose 



