CHAPTER III 

 THE METHOD OF SCIENCE 



Biological sects Facts patent to our senses Facts obscured to them The 

 function of laboratory methods of inquiry The methods by which the facts of the 

 various sciences are observed ' Exact Methods ' The nature of science The 

 scientific value of facts The mental processes by means of which facts are classified 

 Hypotheses and theories The necessity for testing thinking The method 

 by which it is done Induction and deduction Laboratory methods when used 

 as means of discovery and as tests for thinking The common neglect of tests 

 The essence of the experimental method The value of controversy The dis- 

 tinction between facts and theories The legitimate and illegitimate uses of 

 deduction The contrasts between physical, chemical, and biological theories 

 The value of experiment in these sciences Laws of nature Deduction an essential 

 part of the mental processes of rational beings. 



53- fTTAHE reasoning by which we have demonstrated that 

 the development of the individual is a recapitulation 

 of the evolution of the race, is in some measure de- 

 ductive. The facts from which we started our thinking have all 

 been gathered by simple observation. Thus the fact that offspring 

 tend to recapitulate with variations the parental development has 

 been simply observed. The language used by some biological 

 workers indicates an opinion that deduction is illegitimate, or at 

 least unsafe. 1 Others maintain, in effect, that materials furnished 

 by experiment, or some such aid to observation, affords the only 

 safe basis or test for reasoning. 2 The points thus raised, involv- 



1 The statement that deduction any and every sort of deduction is con- 

 sidered illegitimate by any section of scientific workers may be received with 

 incredulity by people who are aware of the part it has played in the creation of 

 science. An acquaintance with medical literature and thought would dispel any 

 doubt. For instance, three years ago there was published a large work (The Food 

 Factor in Disease, by Francis Hare, M.D. ; Longmans, Green and Co.), the preface 

 of which actually consists in an apology for the use of the method an apology 

 for testing thinking. The book, an exceptionally original, thoughtful, and able 

 one, failed, I understand, completely. 



2 " The recognition that only by experimental methods can we hope to place 

 the study of Zoology on a footing with the sciences of chemistry and physics 

 is a comparatively new conception, and one that is by no means admitted as yet 

 by all zoologists. I do not wish to disparage those studies that deal with the descrip- 

 tive and the historical problems of biology. They also afford a wide field for activity, 

 and the more familiar we become with the structure and modes of development 



