98 ROYCE— PRINCIPLES OF THEORETICAL SCIENCE. [April 19, 



theory. On the other hand, the various inter-dependent truths 

 and concepts of theoretical science appear to form a relatively closed* 

 system, where the special forms are infinitely numerous, but where 

 the main types or species are comparatively few. The question in 

 which all students of science ought to be interested, and in which 

 students of philosophy are explicitly interested, is the question as 

 to what common tendency of human activity it is which differ- 

 entiates itself into all these forms. What a thinker does when he 

 puts facts together, and forms a theory, depends of course upon the 

 nature of the facts, in so far as he is trying to describe them, but 

 it also depends upon the nature of his thought, in so far as he 

 can only do for the purposes of thinking, what appeals to his rational 

 interest, and what solves a thoughtful problem. A thinker, how- 

 ever faithful to his facts he means to be, has his needs as a thinker, 

 and his forms of thought are his ways of satisfying his needs. He 

 cannot merely report facts. He must interpret them. His theories 

 are his interpretations. His world of science is his world as inter- 

 preted. It cannot be understood therefore apart from his needs as 

 a thinker. The structure of his theories is the embodiment of these 

 requirements of his own nature as a thinker. That quantitative 

 science, that the principles of geometry, in whatever form they may 

 be stated, that group theory, and that number systems, apply to his 

 world in the regions of which he has a theoretical understanding, all 

 this is due not merely to any outer world, which can exist wholly 

 apart from the thinker, — not merely to such a world, I say, — but 

 certainly also to the nature of the thinker himself. Our study of 

 theoretical science has to be interpreted, then, as a kind of science 

 of a thinker's ways, as an inquiry into what sort of ideal he has, 

 as a study of the meaning of his thoughtful life, of its internal 

 meaning, and of truth, in so far as truth is related to this internal 

 meanino- of the thinker. When we find, as we do, that the forms 

 of thoug-ht are not endlessly variable, but are reducible to a certain 

 range of generically different conceptual structures, we are therefore 

 led to this question which now we face. To what are these 

 thought forms due? What is their unity? 



