LAW, CAUSE 373 



in Chapter XIV, 1 time is often considered at that level of 

 abstraction which neglects its arrow. The question can be 

 settled, therefore, largely on the grounds of convenience. 



Can this peculiar asymmetric feature of nature be located 

 and symbolized ? Clearly, of the three candidates — causal 

 efficacy, temporal asymmetry, and one-way dependence — 

 the second appears most likely. Is there any scientific 

 technique by which the directional feature of time may be 

 ascertained? Is there any method by which the distinction 

 between earlier and later may be recorded? Is there any 

 device by which the scientist is able to distinguish between 

 what Eddington calls a "becoming''' and what he describes 

 as an "unbecoming?" 2 The mere fact that the passage of 

 time can be measured does not suffice. It is true, of course, 

 that t may appear as an independent variable in the func- 

 tional statement of a law. But it occurs in such an equation, 

 in general, only as a lapse of time, i.e., a duration, and one 

 may substitute for it indifferently a positive or a negative 

 value. But if the functional statement is causal, i.e., of the 

 form e = f (c, t), substitution must be made subject to the 

 condition: "t must be positive," or "if t is given a negative 

 value this law describes an unbecoming." The question 

 involves considerations which lead into the very heart of 

 physical science, and hence cannot be raised here. 3 Many 

 believe that in the phenomenon of entropy one has precisely 

 what is required. Nature seems to exhibit a one-way proc- 

 ess which may be described as the increase of randomness. 

 Differences of energy tend to become equalized, hence energy 

 passes from an available to an unavailable form. This is 

 expressed in the second law of thermodynamics by saying 

 that entropy continually increases. For example, if a hot 

 and a cold body are placed in proximity, and the difference 

 in their temperatures immediately recorded, the hot body 

 will cool and the cold body will become warm with the result 



1 Page 288. 2 Nature of the Physical World, p. 94. 



3 See A. S. Eddington, Nature of the Physical World, Chaps. IV, V; R. B. Lindsay 

 and H. Margenau, Foundations of Physics, Chap. V; J. Jeans, New Background of 

 Science (New York: Macmillan, 1933), Chap. VIII. 



