18 INDUCTION. 



6. It is perfectly consistent with the spirit of the method, 

 to assume in this provisional manner not only an hypothesis 



generally admitted, erroneous ; but he was justified in making it, since by de- 

 ducing the consequences of the supposition, and comparing them with the facts 

 of those maladies, he might be certain of disproving his hypothesis if it was ill 

 founded, and might expect that the comparison would materially aid him in 

 framing another more conformable to the phenomena. 



The doctrine now universally received, that the earth is a natural magnet, 

 was originally an hypothesis of the celebrated Gilbert. 



Another hypothesis, to the legitimacy of which no objection can lie, and 

 which is well calculated to light the path of scientific inquiry, is that suggested 

 by several recent writers, that the brain is a voltaic pile, and that each of its 

 pulsations is a discharge of electricity through the system. It has been re- 

 marked that the sensation felt by the hand from the beating of a brain, bears a 

 strong resemblance to a voltaic shock. And the hypothesis, if followed to its 

 consequences, might afford a plausible explanation of many physiological facts, 

 while there is nothing to discourage the hope that we may in time sufficiently 

 understand the conditions of voltaic phenomena to render the truth of the hypo- 

 thesis amenable to observation and experiment. 



The attempt to localize, in different regions of the brain, the physical organs 

 of our different mental faculties and propensities, was, on the part of its 

 original author, a legitimate example of a scientific hypothesis ; and we ought 

 not, therefore, to blame him for the extremely slight grounds on which he often 

 proceeded, in an operation which could only be tentative, though we may 

 regret that materials barely sufficient for a first rude hypothesis should have 

 been hastily worked up into the vain semblance of a science. If there be really 

 a connexion between the scale of mental endowments and the various degrees 

 of complication in the cerebral system, the nature of that connexion 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 hypo- 

 thesis is attended, from the peculiar nature of the phenomena, with difficulties 

 which phrenologists have not shown themselves even competent to appreciate, 

 much less to overcome. 



Mr. Darwin's remarkable speculation on the Origin of Species is another 

 unimpeachable 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 unreasonable 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 ? 



