CHAPTER IV.^ 



PROXlMxiTE DEFINITION OF LIFE. 



§ 24. To those who accept the general doctrine of Evolu- 

 tion, it needs scarcely to be pointed out that classifications are 

 subjective conceptions, which have no absolute demarcations 

 in Nature corresponding to them. They are appliances by 

 which we limit and arrange the matters under investigation ; 

 and so facilitate our thinking. Consequently, when we at- 

 tempt to define anything complex, or make a generalization 

 of facts other than the most simple, we can scarcely ever 

 avoid including more than we intended, or leaving out some- 

 thing that should be taken in. Thus it happens that on 

 seeking a definition of Life, we have great difficulty in find- 

 ing one that is neither more nor less than sufficient. Let 

 us look at a few of the most tenable definitions that have 

 been given. While recognizing the respects in which they 

 are defective, we shall see what requirements a more com- 

 plete one must fulfil. 



* This chapter and the following two chapters originally appeared in Part 

 III. of the Principles of PsycJiology : forming a preliminary w^hich, though indis- 

 pensable to the argument there developed, was somewhat parenthetical. Having 

 now to deal with the general science of Biology before the more special one of 

 Psychology, it becomes possible to transfer these chapters to their proper place. 

 They have been carefully revised. 



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