viii PREFACE. 



the conditions and precautions requisite for accurate ob- 

 servation, for successful experiment, and for the sure 

 detection of the quantitative laws of nature. As it is 

 impossible to comprehend aright the value of quantitative 

 laws without constantly bearing in mind the degree of 

 quantitative approximation to the truth probably attained, 

 I have devoted a special chapter to the Theory of Ap- 

 proximation, and however imperfectly I may have treated 

 this subject, I must look upon it as a very essential part 

 of a work on Scientific Method. 



It then remains to illustrate the sound use of hypo- 

 thesis, to distinguish between the portions of knowledge 

 which we owe to empirical observation, to accidental 

 discovery, or to scientific prediction. Interesting questions 

 arise concerning the accordance of quantitative theories 

 and experiments, and I point out how the successive veri- 

 fication of an hypothesis by distinct methods of experi- 

 ment yields conclusions approximating to but never 

 attaining certainty. Additional illustrations of the general 

 procedure of inductive investigations are given in a 

 chapter on the Character of the Experimentalist, in which 

 I endeavour to show, moreover, that the inverse use of 

 deduction was really the logical method of such great 

 masters of experimental inquiry as Newton, Huyghens, 

 and Faraday. 



In treating Generalization and Analogy, I consider the 

 precautions requisite in inferring from one case to another, 

 or from one part of the universe to another part, the 

 validity of all such inferences resting ultimately upon the 

 inverse method of probabilities. The treatment of Ex- 

 ceptional Phenomena appeared to afford an interesting 

 subject for a further chapter illustrating the various modes 

 in which an outstanding fact may eventually be explained. 

 The formal part of the book closes with the subject of 

 Classification, which is, however, very inadequately treated. 



