proceedings: philosophicaIv society 275 



The following persons have become members of the Academy since 

 the last report in the Journal: 



Mr. Samuel Trask Dana, U. S. Forest Service, Washington, D. C. 



Mr. Earl H. Frothingham, U. S. Forest Service, Washington, D. C. 



Dr. Francis R. Hagner, 900 17th Street, Washington, D. C. 



Mr. Edmund Cecil Harder, care Republic Mining and Manu- 

 facturing Company, 11 11 Harrison Building, Philadelphia, Pennsyl- 

 vania. 



Dr. Alexander Wetmore, Bureau of Biological vSurvey, U. S. 

 Department of Agriculture, Washington, D. C. 



Robert B. Sosman, Corresponding Secretary. 



PHILOSOPHICAL SOCIETY OF WASHINGTON 



824TH MEETING 



The 824th meeting was held at the Cosmos Club, November 22, 19 19. 

 President Humphreys in the chair; 56 persons present. 



Mr. R. C. Tolman presented the first paper on A conception of the 

 business of mathematical physics. 



Like other sciences. Mathematical Physics is in a process of develop- 

 ment from a descriptive to a deductive form. As soon as the main 

 body of a science can be handled deductively, it becomes desirable to 

 pick out the most suitable deductive system for this purpose. 



In performing this task for Mathematical Physics, use should be made 

 of the methods developed for handling deductive systems, by Pierce, 

 Royce, Mrs. Ladd-Franklin, Russell, Whitehead, and Meinong. The 

 universe of discourse in such systems should be generated from a set 

 of indefinables. These indefinables should be chosen so as to be suffi- 

 cient for defining all the concepts in the particular branch of inquiry, 

 and, if possible, should be few in number, simple in nature, familiar to 

 previous workers in the field, independent of each other, of course 

 should be applicable, not merely to the generation of the universe of 

 discourse, but also applicable to the particular field of science under 

 discussion. 



After the definition of the concepts in the universe of discourse has 

 been completed, a set of postulates should be chosen from which the 

 various theorems of the logical system can be deduced. These postu- 

 lates should be chosen so as to be sufficient for deducing all the theorems 

 desired, so as to be consistent with one another, if possible, so as to be 

 independent from one another, few in number, simple in nature, self- 

 evident if possible, familiar, and of course must be true, i. e., applicable 

 to the particular field under investigation. 



For defining the subject matter of Mathematical Physics, the funda- 

 mental relation "is greater than," five fundamental kinds of magni- 

 tude — mass, length, time, charge, entropy — ^and five fundamental 



