LAWS OF NATURE. 



209 



of induction, or test of the correctness 

 of inductions, unless on the hypothesis 

 that some inductions deserving of re- 

 liance have been already made. 



Let us revert, for instance, to one 

 of our former illustrations, and con- 

 sider why it is that, with exactly the 

 eame amount of evidence, both nega- 

 tive and positive we did not reject 

 the assertion that there are black 

 swans, while we should refuse credence 

 to any testimony which asserted that 

 there were men wearing their heads 

 underneath their shoulders. The first 

 assertion was more credible than the 

 latter. But why more credible ? So 

 long as neither phenomenon had been 

 actually witnessed, what reason was 

 there for finding the one harder to be 

 believed than the other ? Apparently 

 because there is less constancy in the 

 colours of animals than in the general 

 structure of their anatomy. But how 

 do we know this ? Doubtless, from 

 experience. It appears, then, that we 

 need experience to inform us in what 

 degree, and in what cases, or sorts of 

 cases, experience is to be relied on. 

 Experience must be consulted in order 

 to learn from it under what circum- 

 stances arguments from it will be 

 valid. We have no ulterior test to 

 which we subject experience in gene- 

 ral ; but we make experience its own 

 test. Experience testifies that among 

 the uniformities which it exhibits or 

 seems to exhibit, some are more to be 

 relied on than others ; and uniformity, 

 therefore, may be presumed, from any 

 given number of instances, with a 

 greater degree of assurance, in pro- 

 portion as the case belongs to a class 

 in which the uniformities have hitherto 

 been found more uniform. 



This mode of correcting one genera- 

 lisation by means of another, a nar- 

 rower generalisation by a wider, which 

 common sense suggests and adopts in 

 practice, is the real type of scientific 

 Induction. All that art can do is 

 but to give accuracy and precision 

 to this process, and adapt it to all 

 varieties of cases, without any 

 tial alteration in its pi'inciple. 



There are of course no means of 

 applying such a test as that above 

 described, unless we already possess 

 a general knowledge of the prevalent 

 character of the uniformities existing 

 throughout nature. The indispen- 

 sable foundation, therefore, of a scien- 

 tific formula of induction must be a 

 survey of the inductions to which 

 mankind have been conducted in un- 

 scientific practice, with the special 

 purpose of ascertaining what kinds 

 of uniformities have been found per- 

 fectly invariable, pervading all nature, 

 and what are those which have been 

 found to vary with difference of time, 

 place, or other changeable circum« 

 stances. 



§ 3. The necessity of such a survey 

 is confirmed by the consideration that 

 the stronger inductions are the touch- 

 stone to which we always endeavour 

 to bring the weaker. If we find any 

 means of deducing one of the less 

 strong inductions from stronger ones, 

 it acquires, at once, all the strength of 

 those from which it is deduced ; and 

 even adds to that strength ; since the 

 independent experience on which the 

 weaker induction previously rested 

 becomes additional evidence of the 

 truth of the better established law in 

 which it is now found to be included. 

 We may have inferred, from historical 

 evidence, that the uncontrolled power 

 of a monarch, of an aristocracy, or of 

 the majority, will often be abused ; 

 but we are entitled to rely on this 

 generalisation with much greater as- 

 surance when it is shown to be a 

 corollary from still better established 

 facts ; the very low degree of eleva- 

 tion of character ever yet attained by 

 the average of mankind, and the little 

 efficacy, for the most part, of the 

 modes of education hitherto practised, 

 in maintaining the predominance of 

 reason and conscience over the sel- 

 fish propensities. It is at the same 

 time obvious that even these more 

 general facts derive an accession of 

 evidence from the testimony which 

 history bears to the effects of des- 







