LOGIC. 



Jatecl and apart from those of all the other 

 sensations. 



Abstraction, or the leaving out parts of 

 ideas or notions ; generalization, or class- 

 ing things together, as possessing the re. 

 inaining distinctive characters ; composi- 

 tion, or the re-assumption of some of the 

 abstracted or rejected ideas, are the vo- 

 luntary acts of the mind, adopted in order 

 to facilitate the useful process of com- 

 parison. Thus we may abstract from bo- 

 dies all ideas but those of structure, and 

 divide them into organized and unorganiz- 

 ed ; or we may take the organized bodies, 

 and call them animals and vegetables ; or 

 we may attend to their place of existence, 

 and call them terrestrial, aquatic, volatile, 

 and the like ; and many of our most use- 

 ful propositions wil' thus, in all our men- 

 tal operations, continue equally general 

 and abstracted. 



In the scientific arrangement of natural 

 objects, philosophers have pursued the 

 course of abstraction, until, by rejecting 

 all the ideas capable of affording the dis- 

 tinctive characters of individuals, they ar- 

 rived at an hypothetical being called sub- 

 stance. Much has been written concern- 

 ing it ; but it will perhaps be attended 

 with the least obscurity to say, that it is 

 supposed to be an independent existence, 

 which serves as the basis or support to 

 those properties which are perceived 

 by our senses ; or, in the words of lo- 

 gicians, it is the subject of modes and ac- 

 cide'nts. 



The modes of substance are those dis- 

 tinguishable objects of sense which might, 

 if separate, produce simple ideas. Thus, 

 softness, fragrance, yellowness, and acidi- 

 ty, are among the modes which co-exist 

 in the subject or substance, lemon. Many 

 distinctions are made in modes. They 

 arc called essential or accidental, abso- 

 lute or relative, &c. The moderns ap- 

 pear to use the words properties of bo- 

 dies, and powers and laws of nature, 

 wilh much more distinctness than the 

 earlier logicians did their modes and ac- 

 cidents. 



Words are intended to be the signs of 

 things, but are very far from being so. If 

 our ideaa were adequate representations 

 of the things which cause them, which 

 they are not ; if they were not of necessity 

 mutilated by abstraction, and there were 

 not a continual exertion in language to 

 emulate the rapidity of thought, then 

 might words obiain the supposed resem- 

 blance. But the boasted extent and per- 

 spicuity of the intellect of man proceeds 

 hut a little beyond the signs and tones of 



those inferior animals who are supposed 

 to have no power of conversing. And 

 even if we could vanquish the insupera- 

 ble difficulties which impede our clear 

 mutual communication, what are the 

 grounds of our knowledge ? they are very 

 limited, and often fallacious. 



Knowledge consists in the determina- 

 tion of those modes of surrounding be- 

 ings which are taken to be permanent, 

 and of those which are observed to vary. 

 The former are chiefly of the nature of 

 quantity and position, and the latter seem 

 resolvable into motion. Mathematical 

 science appears to comprehend the whole 

 of the first ; and the latter, which em- 

 braces by far the greater part of what 

 concerns our existence and well-being, is 

 included in those histories of events upon 

 which we establish our principles of cause 

 and effect Abstraction, or analysis, can 

 give us very clear notions of the subjects 

 of mathematics ; and in these alone it is 

 that we find absolute proof or demonstra- 

 tion. But in all the rest of our knowledge 

 the facts are complex, obscure, and of 

 uncertain evidence ; and the principal, 

 nay the only, ground of our reliance upon 

 our doctrines respecting them is, that out 

 predictions are in many.instances verified. 



Words being constructed and establish- 

 ed by mere usage, are not only inadequate 

 and contracted in their use, but equivo- 

 cal and synonimous ; that is to say, one 

 word may be used to denote several dis- 

 tinct and different things ; as when we 

 speak of a beam of light, a beam of tim- 

 ber, or the beam of a pair of scales ; or, 

 on the contrary, as when we speak of an 

 house, an habitation, or a residence. It 

 must be admitted, however, that there 

 are few synonymes in the practice of 

 those who are masters of a language ; be- 

 cause few words are consecrated by usage 

 to precisely the same meaning. 



Many acute and useful disquisitions 

 have been written upon language and uni- 

 versal grammar. See LANGUAGE. 



Since our idea of a thing must be com- 

 posed or made up of all the simple ideas 

 which that thing can produce by our per- 

 ceptions, and this will for the most part 

 be inadequate, the word, denomination, 

 or name of a thing, must be the sign of 

 that idea, liable to such additional error 

 as may arise from any improper use that 

 may be made of it. And as by abstrac- 

 tion we generalize our ideas and notions, 

 and afterwards comprehend and compare 

 them at our pleasure ; so in the construc- 

 tion of language a like order is followed 

 in words. Thus we may arrange thiifgs, 



