PREFACE ix 



the material has not been actually quoted it has been 

 referred to in footnotes and in bibliographical lists at the 

 ends of the chapters. The aim has been to acquaint the 

 student with the literature of the field, as far as it is avail- 

 able in English, and to indicate where the more detailed 

 discussions of the various problems may be found. Reference 

 material is drawn both from philosophers and from scientists, 

 with, perhaps, undue emphasis on the latter, since sources 

 of this kind are not commonly known to the average student. 

 In view of the textbook character, certain principles have 

 been kept in mind in the selection and arrangement of 

 material. No attempt has been made to give a compre- 

 hensive survey of the field of the philosophy of science. In 

 fact there is some doubt as to whether the phrase "compre- 

 hensive survey' would have any meaning as applied to a 

 field whose limits have not yet been determined. Many 

 readers will be disturbed by what appear to be important 

 omissions. For example, in Part I there is a more or less 

 complete neglect of considerations pertaining to postulate 

 schemes and the formal structure of thinking, and less em- 

 phasis on such topics as classification, analogy, definition, 

 measurement, Mill's experimental methods, and the gen- 

 eral problem of induction, than would seem proper in a 

 book on the philosophy of science. The justification for 

 these omissions and weakened emphases lies in the fact 

 that a definite attempt has been made to avoid duplicating 

 problems usually discussed in courses in logic. The intention 

 has been to write a supplement .to a textbook on logic rather 

 than a substitute for it. Similarly, in Part II the concepts 

 chosen for analysis are meant to be illustrative rather than 

 exhaustive of problems in this field. It so happens that the 

 concepts of the mathematical and physical sciences have 

 undergone the greatest developments, and have been sub- 

 jected to repeated analysis in recent years. They are thus 

 especially valuable as illustrative of certain techniques of 

 abstraction and idealization. An exhaustive consideration of 

 problems at this level would require similar analyses of the 



