MOTIONLESS MOTION 



SOME years ago a modern mathematician who had at 

 that time become interested in AristoteHan-Thomistic 

 philosophy asked me if it would be possible to employ 

 symbolic logic to set forth the proofs for the existence of God. 

 In the attempt to show him that the difficulties in these proofs 

 derived from something other than their logical form, I dis- 

 covered that most of the terms I was using meant something 

 quite different for him. This was particularly true of the term 

 " motion." I, of course, was referring to actus entis in potentia 

 inquantum huiusmodi. When I tried to show him how this 

 notion required an analysis of matter, form, and privation he 

 expressed typical Cartesian astonishment. In the discussion 

 which followed he referred to an idea of motion by a neo- 

 Kantian which he said fairly well expressed his own concept 

 of motion: 



All determination of place ... is a work of the mind: omnis 

 locatio mentis est opus. From this point the way is open to Galileo's 

 foundation of dynamics: for since place has ceased to be something 

 real, the question as to the ground of the place of a body and the 

 ground of its persistence in one and the same place disappears. 

 Objective physical reality passes from place to change of place, to 

 motion and the factors by which it is determined as magnitude. 

 If such a determination is to be possible in a definite way, the 

 identity and permanence, which were hitherto ascribed to mere 

 place, must go over to motion; motion must possess ' being,' that is, 

 from the standpoint of the physicist, numerical constancy. This 

 demand for the numerical constancy of motion itself finds its 

 expression and its realization in the law of inertia.^ 



He also was of the opinion that quite a number of the modern 

 scientists and philosophers would agree, at least in general, 

 with this idea of motion. I was inclined to agree with him on 



^ Ernst Cassirer, Substance and Function (La Salle, Illinois: Open Court Pub- 

 lishing Company, 1923) , p. 362. 



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