MENTAL STATES AND PROCESSES. 109 



necessary. This will appear later on * from the case of 

 Laura Bridgman and the still more remarkable one of 



reason^ meant originally reckoning, casting up, calculation, com- 

 putation, long before it came to mean the so-called faculty of the 

 mind which forms the basis of computation and calculation, judg- 

 ment, understanding, and reason. 



" Secondly, I began my book on the ' Science of Thought' with 

 a quotation from Hobbes, that all our thinking consisted in addition 

 and subtraction, and I claimed the liberty to use the word ' think- 

 ing ' throughout my own book in the sense of combining. Such a 

 definition of thinking may be right or wrong, but, provided a word 

 is always used in the sense in which from the beginning it has 

 been defined, there can at all events be no misapprehension nor 

 just cause of complaint on the part of the critic. 



" What I meant by combination, or by addition and subtraction 

 being the true character of thinking, I explained very fully. 

 'Any book on logic,' I said, 'will teach that all our propositions 

 are either affirmative or negative, and that in acquiring or com- 

 municating knowledge we can do no more than to say that A is B, 

 or A is not B. Now, in saying A is B, we simply add A to the 

 sum already comprehended under B, and in saying A is not B, we 

 subtract A from the sum that can be comprehended under B. And 

 why should it be considered as lowering our high status, if what we 

 call thinking turns out to be no more than adding or subtracting ? 

 Mathematics in the end consist of nothing but addition and sub- 

 traction, and think of the wonderful achievements of a Newton 

 or a Gauss — achievements before which ordinary mortals like 

 myself stand simply aghast.' 



" Prof. Mivart holds that there are but two forms of intellectual 

 activity : (i) Acts of intuition, by which we directly apprehend 

 certain truths, such as, e.g., our own activity, or that A is A ; and 

 (2) Acts of inference, by which we indirectly apprehend others, 

 with the aid of the idea ' therefore.' 



" There is a wide difference between our apprehending our own 

 activity and our apprehending that A is A. Apprehending our 

 own activity is inevitable, apprehending that A is A is voluntary. 

 Besides, the ' therefore ' on which Prof. Mivart insists as a dis- 

 tinguishing feature between the two forms of thought is present in 

 the simplest acts of cognition. In order to think and to say, 



* See below, chapter iii. 



