LOGIC OF PRACTICE OR ART. 



617 



stand to doctrines of science may be 

 thus characterised. The art proposes 

 to itself an end to be attained, defines 

 the end, and hands it over to the 

 science. The science receives it, con- 

 siders it as a phenomenon 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 produced. Art then exa- 

 mines these combinations of circum- 

 stances, and according as any of them 

 are or are not in human power, pro- 

 nounces the end attainable or not. 

 The only one of the premises, there- 

 fore, which Art supplies is the original 

 major premise, which asserts that the 

 attainment of the given end is desir- 

 able. Science then lends to Art the 

 proposition (obtained by a Wviries 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 find- 

 ing it also practicable, converts the 

 theorem into a rule or precept. 



§ 3. It deserves particular notice 

 that the theorem or speculative truth 

 is not rii>e for being turned into a pre- 

 cept until the whole, and not a part 

 merely, of the operation which be- 

 longs to science has been performed. 

 Suppose that we have completed the 

 scientific process only up to a certain 

 point ; have discovered that a parti- 

 cular cause will produce the desired 

 effect, but have not ascertained all 

 the negative conditions which are 

 necessary, that is, all the circum- 

 stances which, if present, would pre- 

 vent its production. If, in this im- 

 perfect state of the scientific theory, 

 we attempt to frame a rule of art, we 

 perform that operation prematurely. 

 Whenever 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 no- 



thing for it but to turn back and 

 finish the scientific process which 

 should have preceded the formation 

 of the rule. We must reopen the 

 investigation to inquire into the re- 

 mainder of the conditions (m which 

 the effect depends ; and only after 

 we have ascertained the whole of 

 these are we prepared to transform 

 the completed law of the effect into a 

 precept, in which those circumstances 

 orcombinations of circumstances which 

 the science exhibits as conditions are 

 prescribed as means. 



It is true that, for the sake of con- 

 venience, rules must be formed from 

 something less than this ideally p)er- 

 fect theory ; in the first place, be- 

 cause the theory can seldom be made 

 ideally perfect ; and next, because, if 

 all the counteracting contingencies, 

 whether of frequent or of rare oc- 

 currence, were included, the rules 

 would be too cumbrous to be appre- 

 hended and remembered by ordinary 

 capacities, on the common occasions 

 of life. The rules of art do not at- 

 tempt to comprise moi-e conditions 

 than require to be attended to in 

 ordinary cases ; and are therefore 

 always imperfect. In the manual 

 arts, where the requisite conditions 

 are not numerous, and where those 

 which the niles do not specify are 

 generally either plain to common ob- 

 servation or speedily learnt from prac- 

 tice, rules may often be safely acted 

 on by persons who know nothing more 

 than the rule. But in the compli- 

 cated affairs of life, and still more in 

 those of states and societies, rules 

 cannot be relied on, without con- 

 stantly referring back to the scientific 

 laws on which they are founded. To 

 know what are the practical contin- 

 gencies which require a modification 

 of the rule, or which are altogether 

 exceptions to it, is to know what com- 

 binations of circumstances would in- 

 terfere with, or entirely counteract, 

 the consequences of those laws : and 

 this can only be learnt by a reference 

 to the theoretic grounds of the rule. 



By a wis© practitioner, therefore, 



