PREFACE vii 



the actual conditions of natural law, under which we exist 

 and promote the knowledge of that truth among our 

 fellows. To do that which is right, we must know that 

 which is true. To act rightly, we must know truly. 



We possess a vast heritage of knowledge handed on 

 to us in tradition and in writings from our father-man in 

 the past. But there are yet immense fields of knowledge 

 to be explored and yet a greater task to be accomplished 

 in spreading the knowledge which we possess, and in 

 persuading all men that it is their right and their duty 

 to acquire it and to enjoy the power and the pleasure 

 which it gives. All must also help, directly or indirectly, 

 in the making of new knowledge. Whilst mankind is 

 still so backward in knowledge and the worship of wisdom, 

 it is idle to indulge in despair of the future. A chief way 

 to increased welfare is still open and untrodden. 



These are big speculations and problems with which 

 to preface a small book. But I am content to offer 

 the small book as a contribution, however restricted, to 

 the spread of a desire for further knowledge of the things 

 about which it tells a possible incitement to serious 

 study of some one or other among them. 



E. RAY LANKESTER 

 June 2</, 1920 



