xxxii PREFACE TO THE SECOND EDITION. 



that Professor Tait adheres to his original opinion that 

 the theory of heat does give evidence of " a beginning." 



I may add that Professor Clerk Maxwell's words seem 

 to countenance the same view, for he says, 1 " This is only 

 one of the cases in which a consideration of the dissi- 

 pation of energy leads to the determination of a superior 

 limit to the antiquity of the observed order of things." 

 The expression " observed order of things " is open to 

 much ambiguity, but in the absence of qualification I 

 should take it to include the aggregate of the laws of 

 nature known to us. I should interpret Professor Maxwell 

 as meaning that the theory of heat indicates the occurrence 

 of some event of which our science cannot give any 

 further explanation. The physical writers thus seem not to 

 be so clear about the matter as Professor Clifford assumes. 



So far as I may venture to form an independent 

 opinion on the subject, it is to the effect that Professor 

 Clifford is right, and that the known laws of nature do 

 not enable us to assign a " beginning." Science leads us 

 backwards into infinite past duration. But that Professor 

 Clifford is right on this point, is no reason why we should 

 suppose him to be right in his other opinions, some of 

 which I am sure are wrong. Nor is it a reason why other 

 parts of my last chapter should be wrong. The question 

 only affects the single paragraph on pp. 744-5 of this 

 book, which might, I believe, be struck out without 

 necessitating any alteration in the rest of the text. It 

 is always to be remembered that the failure of an argu- 

 ment in favour of a proposition does not, generally 

 speaking, add much, if any, probability to the contra- 

 dictory proposition. I cannot conclude without expressing 

 my acknowledgments to Professor Clifford for his kind 

 expressions regarding my work as a whole. 



1 Theory of Heat, 1871, p. 245. 



2, THE CHESTNUTS, 

 WEST HEATH, 



HAMPSTEAD, N.W. 

 August 15, 1877. 



