FALLACIES OF GENERALIZATION. 417 



posteriori, or empiricism properly so called: causation 

 inferred from casual conjunction, without either due 

 elimination, or any presumption arising from known 

 properties of the supposed agent. But bad generali- 

 zation a priori is fully as common ; which* is properly 

 called false theory; conclusions drawn, byway of deduc- 

 tion, from properties of some one agent which is known 

 or supposed to be present, all other coexisting agents 

 being overlooked. As the former is the error of sheer 

 ignorance, so the latter is especially that of instructed 

 minds ; and is -mainly committed in attempting to 

 explain complicated phenomena by a simpler theory 

 than their nature admits of. As when one school 

 of physicians sought for the universal principle of all 

 disease in " lentor and morbid viscidity of the blood/' 

 and imputing most bodily derangements to mecha- 

 nical obstructions, thought to cure them by mechanical 

 remedies*; while another, the chemical school, "ac- 

 knowledged no source of disease but the presence of 

 some hostile acid or alkali, or some deranged condi- 

 tion in the chemical composition of the fluid or solid 

 parts," and conceived, therefore, that " all remedies 

 must act by producing chemical changes in the body. 



* " Thus Fourcroy," says Dr. Paris, " explained the operation of 

 mercury by its specific gravity, and the advocates of this doctrine 

 favoured the general introduction of the preparations of iron, espe- 

 cially in schirrus of the spleen or liver, upon the same hypothetical 

 principle; for, say they, whatever is most forcible in removing the 

 obstruction must be the most proper instrument of cure ; such is 

 steel, which, besides the attenuating power with which it is fur- 

 nished, has still a greater force in this case from the gravity of its 

 particles, which, being seven times specifically heavier than any 

 vegetable, acts in proportion with a stronger impulse, and therefore 

 is a more powerful deobstruent. This may be taken as a specimen 

 of the style in which these mechanical physicians reasoned and 

 practised." Pharmacologia, pp. 38-9. 



VOL. II. 2 E 



