FALLACIES OF GENEKALISATIOK. 



51^ 



human nature at that time and in 

 that particular state of society. If 

 examples are wanted, almost every 

 historical work, until a very recent 

 period, abounded in them. The same 

 may be said of those who generalise 

 empirically from the people of their 

 own country to the people of other 

 countries, as if human beings felt, 

 judged, and acted everywhere in the 

 same manner. 



§ 5. In the foregoing instances, the 

 distinction is confounded between em- 

 pirical laws, which express merely 

 the customary order of the succession 

 of effects, and the laws of causation 

 on which the effects depend. There 

 may, however, be incorrect generali- 

 sation when this mistake is not com- 

 mitted ; when the invebtigation takes 

 its proper direction, that of causes, 

 and the result erroneously obtained 

 purports to be a really causal law. 



The most vulgar form of this fal- 

 lacy is that which is commonly called 

 2wst hoc, ergo propter hoc, or cum hoc, 

 ergo propter hoc. As when it was in- 

 ferred that England owed her indus- 

 trial pre-eminence to her restrictions 

 on commerce ; as when the old school 

 of financiers and some speculative 

 writers maintained that the national 

 debt was one of the causes of national 

 prosperity ; as when the excellence of 

 the Church, of the Houses of Lords 

 and Commons, of the procedure of the 

 law courts, &c., were inferred from 

 the mere fact that the country had 

 prospered under them. In such cases 

 as these, if it can be rendered pro- 

 bable by other evidence that the sup- 

 posed causes have some tendency to 

 produce the effect ascribed to them, 

 the fact of its having been produced, 

 though only in one instance, is of 

 some value as a verification by spe- 

 cific experience ; but in itself it goes 

 scarcely any way at all towards estab- 

 lishing such a tendency, since, admit- 

 ting the effect, a hundred other ante- 

 cedents could show an equally strong 

 title of that kind to be considered as 

 the cause. 



In these examples we see bad 

 generalisation d posteriori, or empiri- 

 cism properly so called : causation in- 

 ferred from casual conjunction, with- 

 out either due elimination, or any 

 presumption arising from known pro- 

 perties of the supposed agent. But 

 bad generalisation d priori is fully 

 as common, which is properly called 

 false theory ; conclusions drawn, by 

 way of deduction, from properties of 

 some one agent which is known or 

 supposed to be present, all other co- 

 existing agents being overl(X)ked. As 

 the former is the error of sheer ig- 

 norance, so the latter is especially 

 that of semi-instructed minds, and is 

 mainly committed in attempting to 

 explain complicated phenomena by a 

 simpler theory than their nature ad- 

 mits of. As when one school of phy- 

 sicians sought for the universal prin- 

 ciple of all disease in "lentor and 

 morbid viscidity of the blood," and 

 imputing most bodily derangements 

 to mechanical obstructions, thought 

 to cure them by mechanical reme- 

 dies ; * while another, the chemical 

 school, "acknowledged no source of 

 disease but the presence of some hos- 

 tile acid or alkali, or some deranged 

 condition in the chemical composi- 

 tion of the fluid or solid parts," and 

 conceived, therefore, that "all reme- 

 dies must act by producing chemical 

 changes in the body. We find Toume- 

 fort busily engaged in testing every 



* "Thus Fonrcroy," says Dr. Paris, "ex- 

 plained the operation of mercury Ijy its 

 specific gravit}', and the advocates of this 

 doctrine favoured the genei-al introduction 

 of the preparations of iron, especially' in 

 schirrus of the spleen or liver, upon the 

 same hypothetical principle ; for. s:iy they, 

 whatever is most forcible in removing tho 

 obstruction must be the most proper in- 

 strument of cure ; such is steel, which, 

 besides the attenuating power with which 

 it is furnished, has still a greater force in 

 this case from the gravity of its ) articles, 

 which, being seven times specifically hea- 

 vier than any vegetable, acts in propor- 

 tion with a stronger impulse, and there- 

 fore is a more powerful deobstruent. Tliis 

 may be taken as a spec men of the styl^ 

 in which these mechanical physicians 

 reasoned and practised."— P/itt?-»i«coiooia, 

 p. 38-39. 



