232 INDUCTION. 



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 lattei'. 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? Ap- 

 parently because there is less constancy in the colors 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 circumstances arguments from it will be valid. We have no 

 ulterior test to which we subject experience in general; but we make ex- 

 perience its own test. Experience testifies, that among th'e 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 num- 

 ber of instances, with a greater degree of assurance, in proportion as the 

 case belongs to a class in which the uniformities have hitherto been found 

 more uniform. 



This mode of correcting one generalization by means of another, a nar- 

 rower generalization 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 va- 

 »rieties of cases, without any essential alteration in its principle. 



There are of course no means of applying such a test as that above de- 

 scribed, unless we already possess a general knowledge of tlie prevalent 

 character of the uniformities existing throughout nature. The indispen- 

 sable foundation, therefore, of a scientific formula of induction, must be a 

 sui'vey of the inductions to which mankind have been conducted in unsci- 

 entific practice ; with the special purpose of ascertaining what kinds of 

 uniformities have been found perfectly invariable, pervading all nature, 

 and what are those which have been found to vary with difference of time, 

 place, or other changeable circumstances. 



§ 3. The necessity of such a survey is confirmed by the consideration, 

 that the stronger inductions are the touch-stone to which we always en- 

 deavor 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 aris- 

 tocracy, or of the majority, will often be abused : but we ai-e entitled to 

 rely on this generalization with much greater assurance when it is shown 

 to be a corollary from still better established facts ; the very low degree 

 of elevation of character ever yet attained by the average of mankind, and 

 the little efllcacy, for the most part, of the modes of education hitherto 

 practiced, in maintaining the predominance of reason and conscience over 

 the selfish 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 despotism. The strong induction be- 

 comes still stronger when a weaker one has been bound up with it. 



On the other hand, if an induction conflicts with stronger inductions, 



