opposed. So then there develops immediately out of these two 

 operations of thought, i.e., the detecting of agreements and the 

 detecting of differences, two of the so-called laws of thought, viz., 

 the law of identity and the law of contradiction, including, likewise, 

 a third which may best be considered as subordinate to and resting 

 upon the other two. The first of these states that throughout the 

 various differences of any concept there remains a certain agreement 

 or a certain constant. The second emphasizes the fact that the 

 differences are so great that the concept can no longer be regarded 

 as the same concept. The first is expressed symbolically as follows: 

 A = A 1 = A'; the second maybe expressed thus of the two pro- 

 positions A is B and A is C, both cannot be true when B and C are 

 contradictory or contrary. The law of excluded middle, sometimes 

 considered as a third law, may be represented by the formula A is 

 either B or C. There is no third possibility, simply because it is 

 here assumed that B and C are all the possibilities, in other words 

 they are contradictories. On account of this limitation this law is 

 seldom operative or helpful in the sciences. The first of these laws 

 rests upon the ascertaining of agreements, the second upon the 

 ascertaining of differences, and the third is really a subsidiary law 

 based upon the other two and so resting finally upon both the as- 

 certaining of agreements and the ascertaining of differences. 



Thus upon these two operations of thought, corresponding to 

 that relation of identity, total or partial, which is one of the basic 

 relations of all judgment forms, rest the above-mentioned laws of 

 thought. 



But not all concepts can be said to stand in a connection of 

 total or partial identity one with the other; there is also a relation 

 of dependence between concepts. We do not predicate identity of 

 any kind between the length of the radius of a circle and its circum- 

 ference, or between the raising of a body to a certain height and the 

 falling of the same, yet there is, we say, a relation of a special kind. 

 This relation grows out of the spacial juxtapositions and temporal 

 sequences which we observe, and, as a result of these, there is formu- 

 lated the law of dependence, or law of sufficient reason or cause and 

 effect, as it is sometimes called. According to this law concepts are 

 united in a relation of dependence. 1 



1 For a more detailed discussion of the psychological origin of the laws of 

 thought, cf. Wundt: Logik, Vol. I, Pp. 548-565, and also his System der Philo- 

 sophie, Pp. 58-75. 



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