CHAPTER V 

 REPRODUCTION AND GROWTH 



I GROWTH 



By growth we mean that a thing increases in size while still 

 retaining its individuality, or identity. 



If it changes in some ways it might become another thing : 

 thus a glacier melts away when it creeps down below a certain 

 level; its stones form a terminal moraine and its ice becomes a river. 



In growing the thing must remain the same thing and by this 

 identity throughout an interval of time we mean that the thing 

 remains accessible to our observation, and may be observed 

 continuously, even if we do not so continue to observe it. It 

 maintains a certain essential form and certain essential relations 

 to other things, this essential form and relations being stated in 

 the definition of the thing even although both the form and the 

 relations may display unessential changes. Thus our bodies are, 

 in a sense, continuous things, identical from moment to moment 

 and always under our observation. They grow and change, but 

 while the growth and change proceed they are still our bodies. 

 Other natural things we regard in the same way. 



By simple growth we mean that a thing increases in size while 

 still retaining its form. Thus a hollow elastic ball that is being 

 inflated with air increases in size, but it still preserves the form 

 of a spherical body. We must regard such simple growth as 

 quite exceptional, for most growing things change in ways that 

 alter their forms. Absolute retention of form while a thing 

 increases in magnitude must be regarded as logically possible. 

 Thus a mathematical function retains its" form while its argument 

 changes, but we have excluded such constructions from our 

 category of natural things. Simple growth, then, is a " limiting 

 process " to which actual processes may approximate. 



By growth with differentiation we mean that a thing increases 

 in size, retains its individuality and identity but changes in form. 

 In this case the changes in form are included in the definition 



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