PREFACE 



I AM quite certain that the majority of my read- 

 ers would have me always stick to natural his- 

 tory themes. I sympathize with them. I am myself 

 never so well pleased as when I can bring them a 

 fresh bit of natural history, or give them a day with 

 me in the fields and woods or along the murmuring 

 streams. Birds and squirrels come home to us all 

 in a way that speculative ideas do not. While writ- 

 ing my more philosophical dissertations, my mind 

 often turns longingly toward the simple outdoor 

 subjects which have engaged me so many years, and 

 doubtless the mind of my reader does also when he 

 is perusiag them. But one cannot always choose at 

 such times. Natural history is a matter of obser- 

 vation; it is a harvest which you gather when and 

 where you find it growing. Birds and squirrels and 

 flowers are not always in season, but philosophy we 

 have always with us. It is a crop which we can 

 grow and reap at all times and in all places, and it 

 has its own value and brings its own satisfaction. 



We are all philosophers, we all delight in finding 

 the reason of things and in tracing the relation of 

 things, and to know, for instance, what part chance 

 plays in oiu- Uves, and what part is played by rigid 

 law, is a worthy and engaging problem. I do not 



