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Mr DE morgan, ON THE SYLLOGISM, No. IV, 



beginner in geometry*, when asked what follows from 'Every A is B,' answers « Every B is 

 A, of course.' That is, the necessary laws of thought, except in minds which have examined 

 their tools, are not very sure to work correct conclusions except upon familiar matter. And 

 above all, relation is a difficulty when the related terms are unusual names, even in the 

 most-j- common cases. 



As the cultivation of the individual increases, the laws of thought which are of most 

 usual application are applied to familiar matter with tolerable safety. • But difficulty 

 and risk of error make a new appearance with a new subject ; and this, in most cases, 

 until new subjects are familiar things, unusual matter common, untried nomenclature 

 habitual ; that is, until it is a habit to be occupied upon a novelty. It is observed 

 that many persons reason well in some things, and badly in others; and this is attributed 

 to the consequences of employing the mind too much upon one or another subject. But 

 those who know the truth of the preceding remarks will not be to seek for what is often, 

 perhaps most often, the true reason. 



Waiving all question about common matter being usually the subject of tolerably 

 good inference, about the assertion that logic, though of some use, does not fully repay its 

 labour, and about the observed fact — the like of which is true in regard to all studies — 

 that learners of logic not infrequently reason no better after instruction than before, — 

 waiving these things, not admitting them, I maintain that logic tends to make the power 

 of reason over the unusual and unfamiliar more nearly equal to the power over the 

 usual and familiar than it would otherwise be. The second is increased ; but the first is 

 almost created. 



An attempt to investigate the forms of thought involved in combination of relations, 

 the results of which are contained in the following pages, has given me personal experience 

 of the truth of the preceding remarks. I have had to work my way through trans- 

 formations as new to my own mind, so far as the separation of form is concerned, as the 

 common moods of syllogism to a beginner in logic. If there be any person who can see 

 at a glance, and with justifiable confidence, what classes of men, including women, are 

 specified in 'the non-ancestors of all non-descendants of Z,' I should not like to submit 

 to his criticism the confusions and blunders through which I arrived at the following 

 results : unless indeed I were able to remind him of some of his own similar experiences. 

 And this could be done with the greatest names in the history of abstract speculation. 



• He is thrown at once into forms of strict reasoning, with 

 unusual matter on which to employ them. Either some logic 

 ought to precede Geometry, with familiar instances ; or some 

 acquaintance with figure by measurement ought to precede the 

 reasoning; or, better than either, both. 



t Though I take the following only from a newspaper, yet 

 I feel confident it really happened : there is the truth of nature 

 about it, and the enormity of the case is not incredible to 

 those who have taught beginners in reasoning. The scene is 

 a ragged school. Teacher. Now, boys, Shem, Ham, and 

 Japheth were Noah's sons; who was the father of Shem, 

 Ham, and Japheth? No answer. Teacher. Boys, you 



know Sir Smith, the carpenter, opposite; has he any sons? 

 Boys. Oh! yes, Sir! there's Bill and Ben. Teacher. 

 And who is the father of Bill and Ben Smith ? Boys. Why, 

 Mr Smith, to be sure. Teacher. Well, then, once more, 

 Shem, Ham, and Japheth were Noah's sons; who was the 

 father of Shem, Ham, and Japheth? A long pause; at last 

 a boy, indignant at what he thought the attempted trick, cried 

 out. It couldn't have been Mr Smith ! These boys had never 

 convened the relation of father and son, except under the 

 material aid of a common surname: if Shem Arkwright, &c., 

 had been described as the sons of Noah Arkwright, part of the 

 difficulty, not all, would have been removed. 



