EXPLANATORY SCIENCE 203 



same as translation from one language into another; for 

 example, all propositions about heat may be translated into 

 propositions about molecules, and if one happens to be 

 more familiar with the latter language than with the former 

 he succeeds by this act in explaining heat. 



It is clear that this conception of explanation is in strict 

 accord with the positivistic conception that entities should 

 not be multiplied beyond necessity. Explanation is a lin- 

 guistic matter — of this one can be sure. Whether it is more 

 than a linguistic matter, i.e., whether there actually are 

 entities referred to by the explanatory symbols — of this one 

 cannot be sure. Hence the principle of caution demands that 

 one refrain from supposing anything which is not certainly 

 known to exist. It is also in strict accord with the positivistic 

 contention that logical deduction is itself merely verbal; 

 conclusion can be obtained from premises by the application 

 of the rules for substitution. Hence premise and conclu- 

 sion, underived proposition and derived proposition, state- 

 ment about explanatory entities and statement about data — 

 both propositions state the same fact, though in different 

 language. 



The realistic reply to this contention follows the lines laid 

 out by Bavink in the quotations given in Chapter VIII, and 

 need not be discussed here. Suffice it to say that for the 

 realist explanation is not merely a matter of language, but an 

 activity involving the actual penetration into the hidden 

 recesses of nature. When one explains he is not exploring 

 language, but nature; nature reveals not only heat but 

 molecules as well, and the problem of science is to determine 

 the precise character of the correlation between these two 

 types of natural entity. This is sharply contrasted with the 

 positivistic attitude which insists that there is only one 

 thing, which may be spoken about either in the language of 

 heat or in the language of molecules. (It is also sharply 

 contrasted with an attitude of extreme realism which in- 

 sists that when heat has been explained it has been ex- 

 plained away, hence only molecules exist.) The realist quite 



