330 



INDUCTION. 



with those of undulations, that there 

 are any actual undulations ; no more 

 than it followed because some (though 

 not so many) of the same laws agreed 

 with those of the projection of- par- 

 ticles, that there was actual emission 

 of particles. Even the undulatory 

 hypothesis does not account for all 

 the phenomena of light. The natural 

 colours of objects, the compound na- 

 ture of the solar ray, the absorption of 

 light, and its chemical and vital action, 

 the hypothesis leaves as mysterious 

 as it found them ; and some of these 

 facts are, at least apparently, more 

 reconcilable with the emission theory 

 than with that of Young and Fresnel. 

 Who knows but that some third hy- 

 pothesis, including all these pheno- 

 mena, may in time leave the undula- 

 tory theory as far behind as that has 

 left the theory of Newton and his 

 successors ? 



To the statement that the condi- 

 tion of accounting for all the known 

 phenomena is often fulfilled equally 

 well by two conflicting hypotheses, 

 Dr. Whewell makes answer that he 

 knows " of no such case in the history 

 of science, where the phenomena are 

 at all numerous and complicated."* 

 Such an affirmation, by a writer of 

 Dr. Whewell's minute acquaintance 

 with the history of science, would 

 carry great aiithority, if he had not, a 

 few pages before, taken pains to re- 

 fute it,+ by maintaining that even the 

 exploded scientific hypotheses might 

 always, or almost always, have been 

 so modified as to make them correct 

 representations of the phenomena. 

 The hypothesis of vortices, he tells 

 us, was, by successive modifications, 

 brought to coincide in its results with 

 the Newtonian theory and with the 

 facts. The vortices did not indeed 

 explain all the phenomena which the 

 Newtonian theory was ultimately 

 found to account for, such as the pre- 

 cession of the equinoxes ; but this 



* P. 371. 



t P. 251 and the wiiola of Appendix G. 



phenomenon was not, at the time, in 

 the contemplation of either party, am 

 one of the facts to be accounted for. 

 All the facts which they did contem- 

 plate we may believe on Dr. Whe- 

 well's authority to have accorded as 

 accurately with the Cartesian h3^po- 

 thesis, iix its finally improved state, as 

 with Newton's. 



But it is not, I conceive, a valid 

 reason for accepting any given hypo- 

 thesis that we are unable to imagine 

 any other which will account for the 

 facts. There is no necessity for sup- 

 posing that the true explanation must 

 be one which, with only our present 

 experience, we could imagine. Among 

 the natural agents with which we are 

 acquainted, the vibrations of an elastic 

 fluid may be the only one whose laws 

 bear a close resemblance to those of 

 light ; but we cannot tell that there 

 does not exist an unknown cause, other 

 than an elastic ether diffused through 

 space, yet producing effects identical 

 in some respects with those which 

 would result from the undulations of 

 such an ether. To assume that no 

 such cause can exist appears to me 

 an extreme case of assumption with- 

 out evidence. And at the risk of 

 being charged with want of modesty, 

 I cannot help expressing astonish- 

 ment that a philosopher of Dr. Whe- 

 well's abilities and attainments should 

 have written an elaborate treatise on 

 the philosophy of induction, in which 

 he recognises absolutely no mode of 

 induction except that of trying hy- 

 pothesis after h3rpothesis until one 

 is found which fits the phenomena ; 

 which one, when found, is to be as- 

 sumed as true, with no other reserva- 

 tion than that if on re-examination it 

 should appear to assume more than is 

 needful for explaining the phenomena, 

 the superfluous part of the assumption 

 should be cut off. And this without 

 the slightest distinction between the 

 cases in which it may be known be- 

 forehand that two different hypo- 

 theses cannot lead to the same result, 

 and those in which, for aught we can 

 ever know, the range of suppositions, 



