GENERAL VIEW OF NATURE AND SCOPE OF LOGIC 23 



character no less from this common constitution of the object of thought than 

 from the mental constitution of the thinking subject. The laws of thought 

 are not purely formal in this sense of being totally and absolutely indepen 

 dent of the nature of its matter or content. They are, however, formal, or 

 non-material, in the sense that they do not vary even when the particular 

 subject-matter of our thought does vary. 



Hence it is that these processes and products of thought may 

 be represented by symbols when they are being analysed for the 

 purpose of illustrating logical laws and principles. The ad 

 vantage thus gained by using brief symbols usually the letters 

 of the alphabet instead of concrete examples, consists not merely 

 in a saving of time but also in an increased facility in fixing our 

 attention on the formal validity of those processes, while the 

 matter of concrete examples would be likely to mislead or at least 

 to distract us. 



11. THE &quot;LAWS OF THOUGHT&quot;. Of the laws brought to 

 light by logical analysis as underlying all our thinking processes, 

 a few are so fundamental that it will be useful to follow the now 

 common practice of setting them forth explicitly at this intro 

 ductory stage. They have been variously described as First 

 Principles of Thought ; Regulative Principles of Thought ; For 

 mal, A Priori^ Laws of Thought ; Postulates of Knowledge. 

 How far those titles are appropriate or misleading will appear 

 from an examination of each of the principles in question. All 

 logicians enumerate at least three : the Principle of Identity, the 

 Principle of Contradiction, and the Principle of Excluded Middle ; 

 to which some add a fourth : the Principle of Sufficient Reason. 

 They are formulated each in a variety of ways. 



1 2. THE PRINCIPLE OF IDENTITY is simply the self-evident 

 truth that Everything is identical with itself ; Everything is its 

 own nature. It is involved in every judgment more directly in 

 every affirmative judgment and demands that throughout every 

 thought-process the objects represented by our concepts and 

 expressed by our terms remain identical with themselves. It 

 thus expresses the unambiguity of the judgment and the immut 

 able character of truth. It does not give us any positive infor 

 mation about a thing, beyond what we possess by thinking of the 

 thing. But we cannot think definitely about anything without 

 mentally marking it off from all that is not itself. Hence the 

 principle is not a bare tautology, capable of being expressed by 

 the statement that A is A. Such a reiterated reference to one 



