Stoney — Natural Science and Ontology. 477 



Sixth Supposition. — Another belief is freely made use of in 

 the Essay, viz. that my organs of sense and parts of my 

 brain are instrumental in introducing sensations into my 

 group of thoughts. 1 



This belief is, however, not a necessary postulate of the inves- 

 tigation. The argument can be stated in language which does 

 not include it ; but the supposition is true, and therefore unobjec- 

 tionable, and it is introduced thus early, because without it we 

 should be obliged to use unfamiliar forms of expression which 

 would be less perspicuous. 



With the same end in view, viz. to attain lucidity, the 

 language of causation is freely used throughout the Essay, but 

 will be found not to involve anything beyond what is included in 

 the fifth of our postulates, until we reach paragraph 22 in the 

 Outline, or p. 510 in the Essay. 



Caution. — It should be distinctly borne in mind that it is not 

 legitimate to infer that causes resemble their effects. As a 

 general rule the presumption is very strongly the other way. 

 When men are forming ontological judgments, they often tacitly 

 assume that causes are like their effects, or suppose that the 

 relations between the causes are of the same kind as those which 

 they find prevailing among the effects, We should be carefully 

 on our guard against these errors. 



The importance of the investigation lies in this, that it enables 

 us to correct other ontological beliefs which are usually entertained 

 with the five enumerated above, but which are found to be no 

 longer tenable along with them ; especially the beliefs that space 

 or space relations have an autic existence (see § 12, p. 480), and 

 that the existing things which are the sources of our sensations 

 are situated in space. The dismissing of these errors and the 

 substitution of correct beliefs for them are an important correc- 

 tion of those ontological beliefs which are commonly accepted by 

 scientific men, and place the inquirer in a much better position for 

 taking his next step in the study of ontology. 



1 In this sentence the terms " brain " and " organs of sense " are to be understood 

 in their autic, not their phenomenal sense. See Diagram III., p. 486. 



202 



