196 ETHICAL ASPECTS OF EVOLUTION 



neither they nor the pistol are to be relied on as giving, 

 with scientific accuracy, the limits of the time. 



The duration, then, of pleasurable states differs from 

 their intensity in the circumstance that it does admit of 

 being measured. But the advantage is only apparent. 

 In the first place, our knowledge of the exact temporal 

 limits gives us no more information about the nature of 

 the mental state contained between them than the area 

 of a sheet of paper does of its colour or its weight. Nor 

 does the clock tell us more about the worth of a pleasure, 

 unless it is supplemented by exact figures for the values 

 and intensities, than it does of the velocity of a train, apart 

 from measurements of the distance traversed. In the 

 computation of pleasures the most essential factors are 

 always estimates, and a total result in which any one of 

 the factors is that is itself nothing better. An allied diffi 

 culty is that it is impossible to ascertain whether the same 

 degree of pleasurable feeling has been maintained without 

 fluctuation from the beginning to the end of the period. 



A still more fatal weakness in the time measurements of 

 pleasures is their wholly incalculable divergence from our 

 subjective estimates of the same periods. This general 

 liability to difference between the estimates and the measure 

 ments of temporal duration has already been noticed ; 

 it is never so great as when the interval has been filled in 

 with pleasure or pain in any degree of more than usual 

 intensity. If we go for a walk, and ask ourselves at any 

 moment how long we have been walking, we can say imme 

 diately, without any explicit process of calculation, that 

 we have been about an hour, or about half an hour. 1 

 Even in this case, where our mental history has been about 

 normal, both as to intensity of feeling and rate of change, 

 the limits of error are very wide. The error may be in 

 calculably greater when what we have passed through is 

 an extremity of pain or pleasure. The highest degrees 

 of both of which we are susceptible fade into unconscious 

 ness, and are destitute of any sense of duration. Ecstasy, 

 1 G. F. Stout, Manual, 387. 



