THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 69 



outset, at any rate, is irrelevant. Since the same question 

 may arise with regard to other concepts which are used to 

 make a certain group of facts intelligible (e.g., with regard 

 to the Objectivity of the " ether " or of " atoms ") it 'is clear 

 that causal and final explanations are to be regarded as on the 

 same level with an indefinite number of others. This being 

 the case it seems hardly worth while to distinguish these 

 particular types of interpretation by a special terminology 

 which simply keeps alive the memory of a controversy which, 

 from the point of view adopted here, has vanished. 



Nevertheless, these traditional terms may very usefully be 

 retained with somewhat new implications.* Thus, without 

 intending any suggestion of " transeunt action " we may use 

 the term " causal law " as a convenient name for statements 

 which exhibit the dependence of the behaviour of a thing upon 

 external conditions. In this sense it is a causal law that two 

 " material particles " in one another's presence, but infinitely 

 remote from all other matter, would exhibit accelerations of 

 their velocities, directed along the straight line joining them, 

 inversely proportional to their masses and to the square of the 

 distance between them. The statement of any such a " causal 

 law " may be called a " causal explanation " of the behaviour of 

 the particles in question, being usefully distinguished by this 

 term from explanation by an " empirical law " which would 

 simply give a formula for the behaviour of a single particle 

 without reference to the behaviour of any other body. But, 

 as a matter of fact, scientific investigators always' endeavour to 

 bring the observed behaviour of bodies under some definite 

 concept or concepts. Thus, in Mechanics, it is sought to 

 describe the behaviour of bodies by means of the concept of 

 the Conservation of Energy, or of Force (Conservation of 

 Momentum), or of Least Action, or one of a number of 



* The first formal suggestion of this use with which I am acquainted 

 is in an interesting article by Ostwald (jun.) and Blossfeldt, Ueber Kausale 

 und finale Erklaruny (Ann. der NaturpJiilosophie, III, 1, pp. Ill et seq.). 



