270 THE FOUNDATIONS OF ZOOLOGY 



out them, lifeless bodies continually do the same. The tide pro- 

 duces changes of matter and energy which would never have been 

 brought about in a tideless ocean, such as the gradual conversion 

 of the earth's motion of rotation into friction between sea and 

 land ; but no one finds, in the friction which has brought the 

 moon to rest upon its axis, anything that might not have been 

 expected. If living bodies did no more than to bring about things 

 which would never happen without them, no one could find in 

 this any essential difference between them and lifeless bodies ; but 

 we do find a most significant difference in the sort of things they 

 bring about, as Aristotle pointed out long ago. " To say what 

 are the ultimate substances out of which an animal is formed is 

 no more sufficient " now than it was two thousand years ago ; for 

 the distinctive things that are brought about by living beings are 

 things that are useful to the beings which bring them about or 

 to their species ; and usefulness implies the continued existence of 

 the user, as distinguished from the things that are used; for it 

 does not consist in the act of use, but in something that comes 

 after. 



The words " survival of the fittest " are meaningless unless 

 the being that survives the selective process is identical with the 

 one that remains fit after the selective process has acted ; and 

 belief in the efficacy of natural selection involves belief in that 

 continuity of life which, in the form we know most intimately, 

 we call personal identity. 



Just so far as natural selection tends to break down the dis- 

 tinction between the contrivances of man and the works of nature, 

 just so far does it show that the distinction between subject and 

 object ; the distinction which is the fundamental problem of all 

 systems of philosophy and the fundamental postulate of most sys- 

 tems of religion ; the distinction between self and not-self ; is co- 

 extensive with life. Since this is so, may we not still say with 

 Paley: "Marks of design are no more accounted for than they 

 were before. Our going back ever so far brings us no nearer to 

 the least degree of satisfaction upon the subject".'' 



As the human child seems, so far as we can ascertain, to gradually 

 discover its continued existence through consciousness and memory 

 of the past, we are apt to think that personal identity implies con- 



