126 SCIENTIFIC METHOD IN PHILOSOPHY 



transitive symmetrical relation to a given term will fulfil 

 all the formal requisites of a common property of all the 

 members of the class. Since there certainly is the class, 

 while any other common property may be illusory, it is 

 prudent, in order to avoid needless assumptions, to 

 substitute the class for the common property which would 

 be ordinarily assumed. This is the reason for the 

 definitions we have adopted, and this is the source of the 

 apparent paradoxes. No harm is done if there are such 

 common properties as language assumes, since we do not 

 deny them, but merely abstain from asserting them. 

 But if there are not such common properties in any given 

 case, then our method has secured us against error. In 

 the absence of special knowledge, therefore, the method 

 we have adopted is the only one which is safe, and which 

 avoids the risk of introducing fictitious metaphysical 

 entities. 



