26 THE PRINCIPLES OF SCIENCE. [ciiap. 



A name is said to denote the object of thouglit to which it 

 may be applied ; it implies at the same time the possession 

 of certain qualities or circumstances. The objects denoted 

 form the extent of meaning of the term ; the qualities 

 implied form the intent of meaning. Crystal is the name 

 of any substance of which the molecules are arranged in 

 a regular geometrical manner. The substances or objects 

 in question form the extent of meaning ; the circumstance 

 of having the molecules so arranged forms the intent of 

 meaning. 



When we compare general terms together, it may often 

 be found that the meaning of one is included in the mean- 

 ing of another. Thus all crystals are included among 

 material substances, and all opaque crystals are included 

 among crystals; here the inclusion is in extension. We 

 may also have inclusion of meaning in regard to intension. 

 For, as all crystals are material substances, the qualities 

 implied by the term material substance must be among 

 those implied by crystal. Again, it is obvious that while 

 in extension of meaning opaque crystals are but a part of 

 crystals, in intension of meaning crystal is but part of 

 opaque crystal. We increase the intent of meaning of a 

 tevui by joining to it adjectives, or phrases equivalent to 

 adjectives, and the removal of such adjectives of course 

 decreases the intensive meaning. Now, concerning such 

 changes of meaning, the following all-important law holds 

 universally true : — When the intent of meaning of a term is 

 increased the extent is decreased ; and vice versa, ^olien the 

 extent is increased the intent is decreased. In short, as one is 

 increased the other is decreased. 



This law refers only to logical changes. The number of 

 steam-engines in tlie world may be undergoing a rapid 

 increase without the intensive meaning of the name being 

 altered. The law will only be verified, again, when there 

 is a real change in the intensive meaning, and an adjective 

 may often be joined to a noun without making a change. 

 Elementary metal is identical with metal; mortal man 

 witli man ; it being a property of all metals to be elements, 

 and of all men to be mortals. 



There is no limit to the amount of meaning which a 

 term may have. A term may denote one object, or many, 

 or an infinite number ; it may imply a single quality, if such 



