SECTION 6. THE PROGRESS OF METHODOLOGICAL THEORY. 49 



examination and verification. Mill almost annihilated the virtues of his 

 Canons, and practically cut himself off from contact with actual scientific 

 work. 



Moreover, a study of Herschel's brilliant Preliminary Discourse, fer- 

 vently admired by Charles Darwin, further reduces Mill's claims, for in 

 the rules suggested by this immediate forerunner of Mill, Mill's whole set 

 of Canons, with almost all its neatness, may be found approximately in 

 Mill's words. This i.s a beautiful illustration of our contention that truth 

 is progressive and represents a growing product of collective endeavour. 

 Mill, in his Autobiography, informs us that, "under the impulse given 

 me by the thoughts excited by Dr. Whewell, I read again Sir John Herschel's 

 Discourse on the Study of Natural Philosophy, and I was able to measure 

 the progress my mind had made, by the great help I now found in this 

 work". (Ch. 6.) Herschel [145.] submits the following "general rules for 

 guiding and facilitating our search, among a great mass of assembled facts", 

 for their common cause: "(1) Invariable connection, and, in particular, 

 invariable antecedence of the cause and consequence of the effect, unless 

 prevented by some counteracting cause. (2) Invariable negation of the 

 effect with absence of the cause, unless some other cause be capable of 

 producing the same effect. (3) Increase or diminution of the effect, with 

 the increased or diminished intensity of the cause, in cases which admit 

 of increase and diminution. (4) Proportionality of the effect to its cause 

 in all cases of direct unimpeded action. (5) Reversal of the effect with 

 that of the cause." In this chapter Herschel speaks of "Agreement", 

 'Concomitant circumstances", and "Residual phenomena", and also judi- 

 ciously illustrates the Method of Difference. With his noted candour Mill 

 admits his debt to Herschel, saying that in this scholar's Discourse, "of 

 all books which I have met with, the four methods of induction are 

 distinctly recognised". (Logic, bk. 3, ch. 9, 3.) 



The following are Mill's Canons (bk. 3, ch. 8): 



First Canon. If two or more instances of the phenomenon under in- 

 vestigation have only one circumstance in common, the circumstance in 

 which alone all the instances agree is the cause (or effect) of the given 

 phenomenon. (See Herschel, Discourse, [146-148.].) 1 



Second Canon. If an instance in which the phenomenon under investi- 

 gation occurs, and an instance in which it does not occur, have every 

 circumstance in common, save one, that one occurring only in the former, 

 the circumstance in which alone the two instances differ is the effect, 

 or the cause, or an indispensable part of the cause, of the phenomenon. 

 (See Herschel, Discourse, [156.].)' 



Third Canon. If two or more instances in which the phenomenon 

 occurs have only one circumstance in common, while two or more in- 

 stances in which it does not occur have nothing in common except the 

 absence of that circumstance, the circumstance in which alone the two 

 sets of instances differ is the effect, or the cause, or an indispensable 

 part of the cause, of the phenomenon. 



Fourth Canon. Subduct from any phenomenon such part as is known 

 by previous inductions to be the effect of certain antecedents, and the 

 residue of the phenomenon is the effect of the remaining antecedents. 

 (See Herschel, Discourse, [158.].) 1 



Fifth Canon. Whatever phenomenon varies in any manner whenever 

 another phenomenon varies in some particular manner, is either a cause 

 or an effect of that phenomenon, or is connected with it through some 

 fact of causation. (See Herschel, Discourse, [145.].) 



These Canons possess at least three grave defects. In dis- 

 cussing the syllogism we pointed out that we are seldom in 

 a position to possess exhaustive data or incontrovertible proof 



1 In the wording of Mill's Canons there is a remarkable similarity to 

 Herschel's sentences. 



