6 INTRODUCTION. 



intellectual operations, only as they conduce to our 

 own knowledge, and to our command over that know- 

 ledge for our own uses. If there were hut one 

 rational being in the universe, that being might be a 

 perfect logician ; and the science and art of logic 

 would be the same for that one person, as for the 

 whole human race. 



4. But, if the definition which we formerly 

 examined included too little, that which is now sug- 

 gested has the opposite fault of including too much. 



Truths are known to us in two ways: some are 

 known directly, and of themselves ; some through the 

 medium of other truths. The former are the subject 

 of Intuition, or Consciousness ; the latter, of Inference. 

 The truths known by intuition are the original pre- 

 misses from which all others are inferred. Our assent 

 to the conclusion being grounded upon the truth of 

 the premisses, we never could arrive at any knowledge 

 by reasoning, unless something could be known ante- 

 cedently to all reasoning. 



Examples of truths known to us by immediate 

 consciousness, are our own bodily sensations and 

 mental feelings. I know directly, and of my own 

 knowledge, that I was vexed yesterday, or that I am 

 hungry to-day. Examples of truths which we know 

 only by way of inference, are occurrences which took 

 place while we were absent, the events recorded in 

 history, or the theorems of mathematics. The two 

 former we infer from the testimony adduced, or from 

 the traces of those past occurrences which still exist ; 

 the latter, from the premisses laid down in books of 

 geometry, under the title of definitions and axioms. 

 Whatever we are capable of knowing must belong to 

 the one class or to the other ; must be in the number 



