296 INDUCTION. 



§ 6. It is perfectly consistent witli the spirit of the method, to assume 

 in this provisional manner not only an hypothesis respecting- the law of 

 what we alreatly know to be the cause, but an hypoihesis respecting 

 the cause itself. It is allowable, useful, and often even necessary, to 

 begin by asking ourselves what cause 7nay have produced the effect, 

 in order that we may know in what direction to look out for evidence 

 to determine whether it actually did. The vortices of Descartes would 

 have been a perfectly legitimate hypothesis, if it had been possible, by 

 any mode of exploration which we could entertain the hope of ever 

 possessing, to bring the question, whether such vortices exist or not, 

 within the reach of our observing faculties. The hypothesis was vicious,- 

 simply because it could not lead to any course of investigation capable 

 of converting it from an hypothesis into a proved fact. The prevailing 

 hypothesis of a luminiferous ether I cannot but consider, with M. Comte, 

 to be tainted with the same vice. It can never be brought to the test 

 of observation, because the ether is supposed wanting in all the proper- 

 ties by means of which our senses take cognizance of external phe- 

 nomena. It can neither be seen, heard, smelt, tasted, nor touched. 

 The possibility of deducing from its supposed laws a considerable 

 number of the phenomena of light, is the sole evidence of its existence 

 that we have ever to hope for; and this evidence cannot be of the 

 smallest value, because we cannot have, in the case of such an hypoth- 

 esis, 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 phenomena; since this is a condition 

 often fulfilled equally well by two conflicting hypotheses ; and if we 

 give ourselves the license of inventing the causes themselves as well as 

 their laws, a person of fertile imagination might devise a hundred 

 modes of accounting for any given fact, while there are probably a 

 thousand more which are equally possible, but which, for want of 

 anything analogous in our experience, our minds are unfitted to con- 

 ceive. But it seems to be thought that an hypothesis of the sort in 

 question is entitled to a more favorable reception, if besides account- 

 ing for all the facts previously known, it has led to the anticipation and 

 prediction of others which experience afterwards verified; as the un- 

 dulatory theory of light led to the prediction, subsequently realized by- 

 experiment, that two luminous rays might meet each other in such a 

 manner as to produce darkness. Such predictions and their Hilfilment 

 are, indeed, well calculated to strike the ignorant vulgar, whose faith 

 in. science rests solely upon similar coincidences between its prophe- 

 cies and- what comes to pass. But it is strange, that any considerable 

 stress should be laid upon such a coincidence by scientific thinkers. If 

 the laws of \k\e propagation of light accord with those of the vibra- 



could only be tentative, though we may regret that materials barely sufficient for a first 

 rude hypothesis should have been hastily worked up by his successors into the vain sem- 

 blance of a science. Whatever 'there may be .of reality in the connexipn between the 

 scale of mental endowments and the various degrees of complication in the ceiehral system 

 (and that there is. some such connexion comparative anatomy seems strongly to indicate), 

 it was in no other way so likely to be brought to light as by framing, in the first instance, 

 an hypothesis similar to that of Gall. But the verification of any such hypothesis is at- 

 tended, from the peculiar nature of the phenomena, with difficulties whi<;h phrenologists 

 have not hitherto shown themselves §ven competent to appreciate, much less to over- 

 come. . " 



