290 ELEMENTS OF SCIENCE 



tension " to the number of common characters which 

 any group we think of may possess. Thus the concept 

 " living creature," has enormous " extension " and but 

 little " intension," while the concept " apple tree " has 

 very great " intension " and but little "extension" 

 since it includes no living creatures whatever save apple 

 trees. Thus the greater the " extension " the less the 

 " intension," and vice versa. 



A concept is denned in logic by means of the lowest 

 genus which contains it, and the difference which 

 separates it oft' from the other species of that genus, as 

 illustrated in Fig. 54. 



For all other matters which concern the first part of 

 logic, the reader is referred to works upon that science. 



The second part of logic treats, as before said, of 

 judgments. What a judgment in itself is, we have 

 already seen.* When expressed in words it is termed 

 an " enunciation " or " proposition." 



A proposition is an expression unambiguously affirm- 

 ing, or denying, one thing of another, and it consists of 

 three parts, two of these are termed respectively (i)the 

 subject; and (2) the predicate ; the third is the copula. 



The subject is that term of which the other is affirmed, 

 as, e.g , in the proposition " virtue is admirable," " virtue " 

 is the subject. The predicate is that term which is affirmed 

 of the other as "admirable" is affirmed of virtue. The 

 copula is the term which connects, or couples, the subject 

 and the predicate, and it is expressed by the term " is." 



Each term may consist of many words, as, e.g, " To rise 

 early in the morning and take a cold bath is healthy." 

 Here, then, the eleven words which precede " is " together 

 constitute one term. 



* See ante, p. 255. 



