546 LOGIC OF THE MORAL SCIENCES. 



menon or effect to be studied, and having investigated its 

 causes and conditions, sends it back to art with a theorem of 

 the combination of circumstances by which it could be pro 

 duced. Art then examines these combinations of circum 

 stances, and according as any of them are or are not in human 

 power, pronounces the end attainable or not. The only one 

 of the premises, therefore, which Art supplies, is the original 

 major premise, which asserts that the attainment of the given 

 end is desirable. Science then lends to Art the proposition 

 (obtained by a series of inductions or of deductions) that the 

 performance of certain actions will attain the end. From 

 these premises Art concludes that the performance of these 

 actions is desirable, and finding it also practicable, converts 

 the theorem into a rule or precept. 



8. It deserves particular notice, that the theorem or 

 speculative truth is not ripe for being turned into a precept, 

 until the whole, and not a part merely, of the operation which 

 belongs to science, has been performed. Suppose that we 

 have completed the scientific process only up to a certain 

 point; have discovered that a particular cause will produce 

 the desired effect, but have not ascertained all the negative 

 conditions which are necessary, that is, all the circumstances 

 which, if present, would prevent its production. If, in this 

 imperfect state of the scientific theory, we attempt to frame a 

 rule of art, we perform that operation prematurely. When 

 ever any counteracting cause, overlooked by the theorem, 

 takes place, the rule will be at fault : we shall employ the 

 means and the end will not follow. No arguing from or about 

 the rule itself will then help us through the difficulty : there is 

 nothing for it but to turn back and finish the scientific 

 process which should have preceded the formation of the rule. 

 We must re-open the investigation, to inquire into the 

 remainder of the conditions on which the effect depends; and 

 only after we have ascertained the whole of these, are we pre 

 pared to transform the completed law of the effect into a 

 precept, in which those circumstances or combinations of cir- 



