PREFACE 



The material in this book, its arrangement, and the method of 

 instruction that it implies are the outcome of some seventeen years 

 of work and thought devoted to the teaching of science to adolescents 

 and to adults. They represent what seems to me at present the 

 kind of knowledge and the kind of attitude that are both wanted 

 and needed, and the kind that it is desirable, from a social point of 

 view, that all of our citizens should acquire sooner or later. 



The point of view throughout is the fact that we have to do with 

 constant changes that need to be understood and that need to be 

 controlled. On the one hand, I have tried to eliminate the anthro- 

 pomorphism that seeks to answer the questions about living things in 

 the form of " Why ? " implying a purposefulness in organisms that 

 is a hindrance rather than an aid to analysis and understanding. On 

 the other hand, I have sought to develop an anthropocentric interest 

 that should humanize the study of living things in terms of appreci- 

 ation and purpose. The understanding of how things work and the 

 solution of problems by means of such understanding are preemi- 

 nently human achievements ; and this view is constantly emphasized 

 from every angle. Man's conquest of his surroundings, through the 

 application of more and more knowledge, through the making of his 

 knowledge more and more trustworthy, furnishes a leading motif. 



In the selection and arrangement of the material I have tried to 

 avoid the specialists' divisions into botany, zoology, etc.; to the stu- 

 dent these are arbitrary and seem to me to confuse rather than to 

 illumine. I have tried to stress the dynamic by speaking of what 

 plants and animals do, and how they do these things, rather than by 

 speaking of the various kinds of organisms that there are, and how 

 to know them apart. So far as possible each main division deals with 

 plants and animals, including man, except where the topic is specifi- 

 cally related to one or another group. So far as possible, each unit of 

 the text is related to something that has been previously learned, or 

 to some outside experience of the reader. I have attempted to suggest 



