FALLACIES OF GENERALIZATION. 365 



towards establishing such a tendency, since, admitting the 

 effect, a hundred other antecedents could show an equally 

 strong title of that kind to he considered as the cause. 



In these examples we see had generalization a 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 had generalization ^ priori is fully as common : 

 which is properly called false theory ; conclusions drawn, hy 

 way of deduction, 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 semi-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 &quot; lentor and morbid 

 viscidity of the blood,&quot; and imputing most bodily derange 

 ments to mechanical obstructions, thought to cure them by 

 mechanical remedies ;* while another, the chemical school, 

 &quot; acknowledged no source of disease but the presence of some 

 hostile acid or alkali, or some deranged condition in the 

 chemical composition of the fluid or solid parts,&quot; and con 

 ceived, therefore, that &quot; all remedies must act by producing 

 chemical changes in the body. We find Tournefort busily 

 engaged in testing every vegetable juice, in order to discover 

 in it some traces of an acid or alkaline ingredient, which 

 might confer upon it medicinal activity. The fatal errors into 



* &quot;Thus Fourcroy,&quot; says Dr. Paris, &quot;explained the operation of mercury 

 by its specific gravity, and the advocates of this doctrine favoured the general 

 introduction of the preparations of iron, especially in scirrhus 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 

 furnished, 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 pro 

 portion 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 phy 

 sicians reasoned and practised.&quot; Phariiiacoloyia, pp. 38-9. 



