LOGIC OF PRACTICE OR ART. 



619 



§ 5. Tlie grounds, then, of every 

 rule of art are to be found in theorems 

 of science. An art, or a body of art, 

 consists of the rules, together with as 

 much of the speculative propositions 

 as comprises the justification of those 

 rules. The complete art of any mat- 

 ter includes a selection of such a por- 

 tion from the science as is necessary 

 to show on what conditions the effects 

 which the art aims at producing de- 

 pend. And Art in general consists 

 of the truths of science, arranged in 

 the most convenient order for prac- 

 tice, instead of the order which is the 

 most convenient for thought. Science 

 groups and arranges its truths so as 

 to enable us to take in at one view as 

 much as possible of the general order 

 of the universe. Art, though it must 

 assume the same general laws, follows 

 them only into such of their detailed 

 consequences as have led to the for- 

 mation of rules of conduct, and brings 

 together from parts of the field of 

 science most remote from one another 

 the truths relating to the production 

 of the different and heterogeneous 

 conditions necessary to each effect 

 which the exigencies of practical life 

 require to be produced.* 



Science, therefore, following one 

 cause to its various effects, while art 

 traces one effect to its multiplied and 

 diversified causes and conditions, 

 there is need of a set of intermediate 

 scientific truths, derived from the 

 higher generalities of science, and 

 destined to serve as the generalia or 

 first principles of the various arts. The 

 scientific opei-ation of framing these 

 intermediate principles, M. Comte 

 characterises as one of those results 

 of philosophy which are reserved for 

 futurity. The only complete example 

 which he points out as actually rea- 

 lised, and which can be held up as a 

 type to be imitated in more important 

 matters, is the general theory of the 



• Professor Bain and others call the se- 

 lection from tlie truths of science made for 

 the purposes of an art, a Practical Science ; 

 and coufiue the name Art to the actual 

 rules. 



art of Descriptive Geometry, as con- 

 ceived by M. Monge. It is not, how- 

 ever, difficult to understand what the 

 nature of these intermediate principles 

 must generally be. After framing the 

 most comprehensive possible concep- 

 tion of the end to be aimed at, that 

 is, of the effect to be produced, and 

 determining in the same comprehen- 

 sive manner the set of conditions on 

 which that effect depends, there re- 

 mains to be taken a general survey of 

 the resources which can be com- 

 manded for realising this set of con- 

 ditions ; and when the result of this 

 survey has been embodied in the few- 

 est and most extensive propositions 

 possible, those propositions will ex- 

 press the general relation between the 

 available means and the end, and will 

 constitute the general scientific theory 

 of the art, from which its practical 

 methods will follow as corollaries. 



§ 6. But though the reasonings 

 which connect the end or purpose of 

 every art with its means belong to 

 the domain of Science, the definition 

 of the end itself belongs exclusively to 

 Art, and forms its peculiar province. 

 Every art has one first principle, or 

 general major premise, not borrowed 

 from science ; that which enunciates 

 the object aimed at, and aflBrms it to 

 be a desirable object The builder's 

 art assumes that it is desirable to have 

 buildings ; architecture, (as one of the 

 fine arts,) that it is desirable to have 

 them beautiful or imposing. The hy- 

 gienic and medical arts assume, the 

 one that the preservation of health, 

 the other that the cure of disease, 

 are fitting and desirable ends. These 

 are not propositions of science. Pro- 

 positions of science assert a matter 

 of fact : an existence, a co-existence, 

 a succession, or a resemblance. The 

 propositions now spoken of do not as- 

 sert that anything is, but enjoin or 

 recommend that something should be. 

 They are a class by themselves. A 

 proposition of which the predicate is 

 expressed by the words ought or should 

 he, is genericaDy different from one 



