60 ETHICAL ASPECTS OF EVOLUTION 



spondence could be detected between pleasure and ad 

 vantage, the relation would still be out of reach of exact 

 demonstration. 



The same defect puts it out of our power to make any 

 exact or objectively valid comparison between pleasures 

 and pains, or pains and disadvantages, or single pleasures 

 and pains and other pleasures and pains. We do indeed 

 compare all these and act on the results of our comparison ; 

 otherwise we could not exist ; but we can never prove, 

 either to our own satisfaction or to the satisfaction of others, 

 that our judgements are correct. That is always a matter 

 of faith. Without valid single judgements there can be no 

 valid general laws; and, where every factor in the com 

 putation is undetermined, there can be no valid judgements 

 at all. Even so extreme an assertion as Mille piaceri non 

 vagliono un tormento admits neither of proof nor of dis 

 proof. Indeed, when we proceed from comparing one 

 pleasure with another to comparing pleasures with pains, 

 our position becomes still more difficult. Not only are 

 we unable to measure either, but we are not by any means 

 certain that they belong to the same series or group of feelings. 

 For all we know they may be quite disparate, and it may 

 be as impossible to reduce them to a common denominator 

 as to state a furlong in terms of a bushel of wheat. 



Again, if pleasure is to be regarded as practically conducive 

 to welfare, and not merely as an idle signal, it must have 

 a definite influence on human action. That implies that 

 it is a link in a chain of natural causality. But the principle 

 of conservation of energy requires that all such links must 

 be modes of force, acting in time and space, and, like all the 

 factors in the total sum of cosmic energy, capable of exact 

 measurement. That we are not now in a position to repre 

 sent pleasure as a force, capable of being stated in terms 

 of other forces, such as light and electricity, is quite certain ; 

 that we ever shall be is a gratuitous assumption, unsupported 

 by the past history of thought, and with no other warrant 

 than the dreams of men of science. For the present, at 

 any rate, we are debarred by the above closely allied con- 



