318 



pursuing the clews here suggested, to a considerable extent, when 

 the investigation is employed exclusively upon one object. We 

 know nothing of the efficient causation of diseases: we reason upon 

 this causation on grounds of analogy; but the causes concerned can 

 never be specified, because they are not objects cognizable to the 

 senses. We aspire occasionally to the removal of remote causes, as 

 when we take blood from a vein, or remove a stone from the bladder, 

 but in these cases, the latter of which is the least equivocal, we are 

 ignorant of the efficient or real cause : a stone in the bladder, it may 

 be said, is the cause of irritation; remove this stone, and the cause 

 is removed, and the irritation ceases; very true: the cause is re- 

 moved with the stone, but what is the cause? The effect of the 

 stone is to produce a certain state, which we call one of irritation of 

 animal properties; these properties can be modified only by an 

 union or combination of other properties: it would be absurd to say 

 that a stone combined with life, and modified its identity. The 

 efficient cause must be looked for in the properties of the stone, 

 which are related with life; what these properties are we cannot 

 define, because they, like the properties with which they are related, 

 are not cognizable to the senses. Indeed, in this case the distinction 

 remains to be drawn and the grounds of it stated, whether the rela- 

 tion of the properties of the stone is direct or mediate; whether by 

 latent properties common to matter related with life (such as are 

 indicated by food, or nutritious substances), to be classed neither as 

 chymical nor mechanical; or whether by simple gravity modified in 

 its agency by shape and asperities, and related with the spirit by 

 means only of a primitive relation with the mechanical structures, 

 with which the spirit is in alliance. It suffices, however, in these 

 cases, without looking for true or efficient causes, that we are 

 enabled to remove these causes by our knowledge of their alliance 

 with sensible substances. 



28. The sum of our experience (or, perhaps more correctly, of 

 our information, for it is mostly inferential), is, 



1st, That some remedies will cure some diseases, and that others 

 will not. 



2nd, That the employment of remedies is founded upon 

 analogy; that is, such diseases have been cured by such remedies, 

 and, in agreement with the analogy, we employ the same remedies 

 when we meet with the same diseases. The practice of medicine 

 upon this principle has been called empirical. The difference be- 

 tween empirical practice and that which is distinguished as scientific 

 is, that the analogy in the first is general, and in the latter it is par- 

 ticular. The empiric founds his practice on a partial observance of 

 the analogy of symptoms, and on the general results of remedies; 

 the man of science does not employ remedies simply because they 

 Lave been found to cure, but he employs them with a view to a par- 

 ticular mode of operation. The empiric would give a purgative where 

 disease was accompanied by long-accustomed torpor of the bowels : 

 the man oi 'science would perhaps give a purgative iu the same case, 



