theory of inorganic evolution and Darwin's theory, are free from un- 

 intelligible elements. 



We have noted that the theory of ions had involved in its reasoning 

 one unintelligible element; that the dependence of chemical quality 

 upon the mechanical structure of the atom was not known to be a 

 fact and in the present state of science is unexplainable. It is evident 

 that this impairs the believability of the theory. In order to believe 

 the theory, we must infer that chemical quality is dependent upon me- 

 chanical structure, and this is the more difficult to do just because we 

 cannot explain such a relationship. However, the theories most com- 

 plex in this respect, the theories possessing the most unintelligible ele- 

 ments, were the theories of Locke and Hyslop. These two were also 

 the least believable of the theories examined. In dealing with the 

 question of the relation between method of procedure and believability, 

 we discovered that the method of assumption gave rise to unintelligible 

 elements in these theories, and that because of these elements the 

 theories lacked believability. It will, therefore, be unnecessary to show 

 here that theories, complex in this respect, will lack believability. It 

 will hardly be disputed that when a theory requires an inference to be 

 made, that inference will be less readily made, when it is of the ex- 

 istence of unintelligible things. The theories possessing most such in- 

 comprehensible elements, like the theories of Locke and Hyslop, are 

 the least believable. Therefore, we conclude that there is an inti- 

 mate relationship between the believability of a theory and its com- 

 plexity, when complexity refers to the existence of unintelligible ele- 

 ments. 



THE VERIFIABILITY OF THEORIES. 



To verify means to show the truth of. We shall first consider the 

 question of how theories are verified and on what their verifiability de- 

 pends. We have found that there are two distinct types of theories; 

 those of definition and those of origin. How are theories of definition 

 verified? The theory that matter is electrical is a theory of definition, 

 and we shall consider how its truth may be shown. We can deter- 

 mine by observation and experiment the essential qualities of elec- 

 tricity. To demonstrate that matter is electrical, we must show that 

 it has the same essential qualities as electricity. An investigation of 

 matter will reveal its qualities, and they can then be compared with 

 those of electricity. The characteristic quality of matter is found to be 

 inertia. By experiment we show that electricity possesses this same 

 quality. Therefore, electricity is matter, or matter is electricity. 

 Here then, we see that verification consists in showing that the facts 

 affirmed by the theory are true by experimentally manifesting them in 

 experience, or gaining evidence for their existence. Once the theory 



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