GENERAL VIEW OF NATURE AND SCOPE OF LOGIC. 27 



that they &quot; do not profess to give any material knowledge, and their validity 

 is in no way dependent on material conditions,&quot; ] i.e. on any special conditions 

 or changes of the particular subject-matter we may be thinking about. &quot; The 

 three laws,&quot; writes Dr. Keynes, 2 &quot; may be expressed by these formulas : 1 

 affirm what I affirm, and deny what I deny ; If I make any affirmation I 

 thereby deny its contradictory ; IJ I make any denial, I thereby affirm its 

 contradictory &quot;. 



&quot; It follows that we cannot make any progress in material knowledge ex 

 cept in subordination to these laws. But at the same time they do not 

 directly advance our knowledge of things. They are distinctly laws relating 

 to judgments, and not directly to the things about which we judge.&quot; 



The close relation of these two the subjective and objective, the 

 formal and material aspects in the principles in question, will be still more 

 evident in a fourth principle : the Principle of Sufficient Reason. In this 

 principle the material or real side the reference to reality is so prominent, 

 and so overshadows the reference to thought, that the advisability of ranking 

 the latter with the three foregoing principles in an introduction to logic has 

 been sometimes questioned. We will merely state it here, deferring a fuller 

 treatment of it to Induction. 



1 6. THE PRINCIPLE OF SUFFICIENT REASON, as formu 

 lated by Leibniz (Monadolagie, 31-39), states that &quot; no fact 

 can be found to be real, no proposition true, without a sufficient 

 reason why it is in this way rather than in another,&quot; or, &quot; whatever 

 exists, or is true, must have a sufficient reason why the thing or 

 proposition should be as it is and not otherwise &quot;. The principle 

 contains very explicitly a double reference : firstly, to our thoughts, 

 judgments, reasoning processes ; secondly, and more funda 

 mentally, to the reality itself with which such mental processes 

 are concerned. In its first or more formal aspect under which 

 it says that every judgment must have a reason it is at the bot 

 tom of all our reasoning processes, giving explicit expression to 

 the necessity with which consequent follows from antecedent, con 

 clusion from premisses. But since every judgment cannot have 

 for its reason an anterior judgment, since we must start from 

 judgments which do not depend on others, we are entitled to ask 

 what sufficient reason have we for assenting to these : to which 

 the only answer is that the reality which is the object of those 

 self-evident judgments compels or constrains us to judge as we do 

 about it. This &quot; constraining power &quot; which is described by some 

 modern philosophers as &quot; the characteristic of the real,&quot; 3 scholastic 

 philosophers have always called &quot; objective evidence &quot;. For the 



1 KEYNES, op. cit., p. 463. 2 ibid. 



3 WELTON, Manual of Logic, vol. i., Introd., p. i. 



