110 PERSONALITY 



and development. But reality, we are accus 

 tomed to think, is something apart from this 

 temporary and one-sided view of it, so that 

 what we really see is simply a world of matter 

 and energy, as described by the physical 

 sciences. 



If we look back, however, at the history 

 of the gradual development of our scientific 

 ideas, we find that they have one and all 

 sprung out of the needs of practical life. The 

 tradesmen who devised and used the balance, 

 and the engineers who measured in foot 

 pounds and horse-power, had practical ideas of 

 mass and energy long before men of science 

 definitely formulated and extended these 

 conceptions. The sciences are built up on 

 ideas which have their roots in practical 

 human needs. These ideas are changing and 

 developing with human progress, and never 

 escape from being anthropocentric. When 

 separated from the mother earth of human 

 experience they cease to live ; and this is so 

 whether the experience is that of ordinary 

 practical activity or of laboratory experiments. 

 We cannot separate our world from our 

 interest in it. What we see in it is deter- 



