386 METHODOLOGY OF SCIENCE 



beyond the immediately given content of present perception. In 

 introducing it we have in mind, moreover, that the foundations of 

 every possible interpretation of nature possess a dynamic character, 

 just because all empirical thought, in this field as well, is subordinate 

 to the causal law. This must be admitted by any one who assumes 

 as indispensable aids of natural science the mechanical figures 

 through which we reduce the events of sense perception to the mo- 

 tion of mass particles, that is, through which we associate these 

 events with the elements of our visual and tactual perception. All 

 formulations of the concept of mass, even when they are made so 

 formal as in the definition given by Heinrich Hertz, indicate dynamic 

 interpretations. Whether the impelling forces are to be thought of 

 in particular as forces acting at a distance or as forces acting through 

 collision depends upon the answer to the question whether we have 

 to assume the dynamic mass particles as filling space discontinuously 

 or continuously. The dynamic basis of our interpretation of nature 

 will be seen at once by any one who is of the opinion that we can make 

 the connection of events intelligible without the aid of mechanical 

 figures, for instance, in terms of energy. 



Thus it results that we interpret the events following one another 

 immediately and uniformly as causes and effects, by presupposing 

 as fundamental to them forces that are the necessary means of their 

 uniformity of connection. What we call "laws" are the judgments 

 in which we formulate these causal connections. 



A second and a third consequence need only be mentioned here. 

 The hypothesis that interprets the mutual connection of psychical 

 and physical vital phenomena as a causal one is as old as it is natural. 

 It is natural, because even simple observations assure us that the 

 mental content of perception follows uniformly the instigating 

 physical stimulus and the muscular movement the instigating 

 mental content which we apprehend as will. We know, however, 

 that the physical events which, in raising the biological problem, we 

 have to set beside the psychical, do not take place in the periphery of 

 our nervous system and in our muscles, but in the central nervous 

 system. But we must assume, in accordance with all the psycho- 

 physiological data which at the present time are at our disposal, that 

 these events in our central nervous system do not follow the cor- 

 responding psychical events, but that both series have their course 

 simultaneously. We have here, therefore, instead of the real relation 

 of dependence involved in constant sequence, a real dependence of 

 the simultaneity or correlative series of events. This would not, of 

 course, as should be at once remarked, tell as such against a causal 

 connection between the two separate causal series. But the contested 

 parallelistic interpretation of this dependence is made far more 

 probable through other grounds. These are in part corollaries of the 



