THE RELATION OF MIND AND BODY 297 



our data are, at best, of only a limited practical value. If we 

 weigh an animal or man, we obtain data which may be of great 

 practical value; but what are we weighing? It is not the 

 living body, because it includes the contents of the alimentary 

 canal and other cavities and perhaps the clothes : it also includes 

 deposits of fat, water and other material stored in the body, 

 either within or outside of living cells : also liquids such as the 

 blood plasm and lymph-deposits, of inorganic matter in the 

 bones and apparently lifeless organic matter in the connective 

 tissues and elsewhere. When we investigate metabolism or 

 chemical constitution of material or any other process or state 

 occurring in the body, similar questions have to be faced ; and 

 we begin to realise that in investigating biological questions 

 from the standpoint of physics and chemistry alone we are 

 dealing with a collection of abstractions from reality and that 

 we can do better by using a less abstract working hypothesis. 



These physical investigations, like all scientific investiga- 

 tions, have nevertheless a very great practical value : for though 

 they are partial and one-sided they give us the best insight 

 we can for the time get as regards countless matters of detail 

 in our experience. The great mistake, leading to such con- 

 clusions as that living organisms are physico-chemical mechan- 

 isms or that conscious behaviour is nothing but physico-chemical 

 change accompanied by consciousness, is to lose sight of the 

 wider point of view which shows us that in physical or indeed 

 any scientific investigation we are always dealing with partial 

 aspects of reality. 



We can arrange the sciences in a certain order, according 

 as they deal with more or less abstract and one-sided aspects 

 of reality. The purely mathematical sciences come lowest in 

 this order ; next to them come the physical sciences ; then 

 biology ; whilst psychology and ethics deal with what is least 

 abstract. But if the mathematical sciences stand lowest in 

 one way, in another way they stand highest, as they have the 

 widest and most general field of application ; and all knowledge 

 and practice involve quantitative treatment. 



Between body and mind there is no interaction, simply 

 because the body, more fully understood, is the mind. From 

 the physical and chemical standpoint a man is about 70 kilo- 

 grammes of material with a certain configuration, properties and 

 internal movements : this material consisting of a great variety 



