Stoney — Natural Science and Ontology. 483 



The great machine has moved, and the shadows which it casts have 

 undergone change. But the cause of this change is to he sought, 

 not in any power which the shadows have to operate on one 

 another, but in whatever has brought about the motion of the 

 machine. Physical causes are but causes conceived of as operating 

 between the shadows, and are but symbols in their relation to the 

 true causes that have operated between the auta of the sense- 

 compelling Universe. They are, nevertheless, entitled to be pro- 

 nounced real (as being based on reality and a legitimate supplement 

 of the phenomenal hypotheton) whenever the indirect causal con- 

 nection represented in the diagram actually exists. 



26. The commonly received noiimenal hypothesis that material 

 substances exist and have space relations to one another is dis- 

 credited by the investigation. The author has elsewhere put 

 forward in substitution for it the noiimenal hypothesis that all 

 auta are thoughts, sense-compelling auta as well as egoistic. 

 The evidence for this monistic hypothesis is glanced at, but not 

 fully discussed, in the essay of which this is an abstract, since 

 neither the argument nor the conclusions of the essay depend on it. 



27. The main steps of the argument are presented in a dia- 

 grammatic form in the first of the following diagrams. 



28. The conclusion is stated in the paragraph which begins at 

 the middle of p. 519 of the essay. 



