THE PHILOSOPHY OF BIOLOGY 



CHAPTER I 



THE CONCEPTUAL WORLD 



LET us suppose that we are walking along a street in 

 a busy town ; that we are familiar with it, and all 

 the things that are usually to be seen in it, so that 

 our attention is not likely to be arrested by anything 

 unusual ; and let us further suppose that we are 

 thinking about something interesting but not intel- 

 lectually difficult. In these circumstances all the 

 sights of the town, and all the turmoil of the traffic 

 fail to impress us, though we are, in a vague sort of 

 way, conscious of it all. Electric trams approach and 

 recede with a grinding noise ; a taxicab passes and 

 we hear the throb of the engine and the hooting of the 

 horn, and smell the burnt oil ; a hansom comes down 

 the street and we hear the rhythmic tread of the horse's 

 feet and the jingle of the bells ; we pass a florist's 

 shop and become aware of the colour of the flowers 

 and of their odour ; in a cafe a band is playing " rag- 

 time." There are policemen, hawkers, idlers, ladies 

 with gaily coloured dresses and hats, newsboys, a crowd 

 of people of many characteristics. It is all a flux of 

 experience of which we are generally conscious without 

 analysis or attention, and it is a flux which is never 

 for a moment quite the same, for everything in it 

 melts and flows into everything else. The noise of 

 the tram-cars is incessant, but now and then it becomes 



