EVOLUTION 41 



observational work. The two types of mind are different, 

 and both are wanted. In Darwin alone do we meet with 

 the unique example of the combination of the two faculties 

 in the same individual. But Darwin, be it remembered, 

 philosophized only within the domain of organic Evolu- 

 tion, while Spencer's Philosophy embraced the whole 

 domain of Evolution. 



If justification for the use of the deductive method by 

 those who have not themselves contributed the data be 

 looked for among the sciences, a good case can be made 

 out. That which is sanctioned within the narrower con- 

 fines of the special sciences is no less justifiable for Science 

 as a whole. In those sciences in which the observed facts 

 are capable of quantitative expression, such as astronomy, 

 physics, mechanics (in the abstract sense), &c., con- 

 clusions of the greatest general importance have been 

 arrived at deductively by men who have never carried 

 out an experiment or made an observation. It is, of 

 course, admitted that in these sciences the data are 

 capable of being dealt with by the most powerful and the 

 most perfect of all deductive weapons — the mathematical. 



Now what Spencer did, virtually amounted not only to 

 a vindication of the right of all the sciences tb stand on 

 the same footing as regards their mode of treatment, but 

 to the insistence on the necessity for the use of the deduc- 

 tive method as a means of advancement in the biological 

 sciences in the same sense that it is a recognized method 

 in the physical sciences. He may not state so expHcitly 

 in his writings, but there can, I think, be no doubt that 

 this is a legitimate interpretation of his teaching. His 

 attempt was confessedly a bold one in view of the fact 

 that in his time the biological sciences were not amenable 

 to quantitative treatment, and that their data had not 

 been brought within the sphere of symbolical reasoning. 

 It is in fact only in comparatively recent times that 

 biological data have been dealt with quantitatively on 

 a sufficient scale and with sufficient precision to enable 

 them to be handled deductively. I refer, of course, to 



