THE 'FUNDAMENTAL LAWS OF THOUGHT.' 3-13 



Our reasoning faculties are very feeble; we can only 

 arrive at a knowledge of obscure truths and laws by labo- 

 rious intellectual processes ; we have to study facts again 

 and again many times over, and come to them repeatedly in 

 a new frame of mind, in order to discover the truths they 

 contain ; and even then we are only able to extract a 

 minute proportion of the truth that is in them ; and 

 much of the knowledge we do extract we distort with 

 our previous mental errors. 



An indispensable condition of drawing correct con- 

 clusions in science is consistency with the actual truths of 

 nature. Erroneous beliefs prevent correct thought; we 

 cannot, by proper reasoning processes, draw true conclusions 

 from them except by accident, and therefore true belief is 

 a necessary condition for obtaining trustworthy conclusions 

 by means of truly logical inferences. Before we begin to 

 reason upon a scientific question, we must also clear the 

 subject of all indifferent and unnecessary elements, because 

 all unnecessary ideas confuse our minds. 



The minds of all intelligent persons act in accordance 

 with what are called the ' fundamental laws of thought,' 

 viz. 1. The law of identity; illustrated by the statement, 

 whatever is, is. 2. The law of contradiction ; illustrated 

 by the proposition, a thing cannot be and not be ; and, 

 3. The law of duality ; exhibited in the statement, a thing 

 must either be or not be. 1 These three axioms may, per- 

 haps, be more properly called ' laws of nature,' and ' rules 

 of thought' based upon them, because they agree with our 

 universal experience, and with the modes in which we 

 have been led to think by that experience. As agreement 

 with nature is the sole test of scientific belief, these 

 three logical axioms must be assumed and admitted in 



1 Thomson, Outline of the Lam* of Thought, p. 211. Jevons, Prin- 

 ciples of Science, vol. i. 2nd edition, p. 5. 



