404 LOGIC: OR, THE RIGHT 555E OP REASON. cerning the subject ; so in this proposition, a spirit is not an animal, we exclude all sorts and kinds and particular animals whatsoever from the idea of a spirit. From these two last remarks we may derive this inference, that we ought to attend to the entire comprehension of our ideas, and to the universal extension of them, as far as we have pro - per capacity for it, before we grow too confident in our affirming or denying any thing which may have the least darkness, doubt or difficulty attending it : it is the want of this attention that be- trays us into many mistakes. SECT. III. Of the Opposition and Conversion of Propositions. ANY two ideas being joined or disjoined in various forms will afford us several propositions : all these may be distin- guished according to their quantity and their quality into four, which are marked or denoted by the letters, A, E, I, O, thus : A Universal Affirmative. E Universal Negative. denotes a I Particular Affirmative. O Particular Negative. according to these old Latin rhymes- - Asserit A, Negai E, verum generaliter Anzbee. Asserit I, Negat O, sed particulariter Ambo. This may be exemplified by these two ideas, a Vine and a Tree. A Every Vine is a Tree. E No Vine is a 'free. I Some Vine is a Tree. O Some Vine is not a Tree. The logicians of the schools have written many large trifles concerning the opposition and conversion of propositions. It will be sufficient here to give a few brief hints of these things,. that the learner may not be utterly ignorant of them. Propositions which are made of the same subject and pre- dicate are said to be opposite, when that which is denied in one is affirmed in the other, either in whole or in part, without any consideration whether the propositions be true or no. If they differ both in quantity and quality they are called contradictory ; as, .A Every Vine is a Tree. ¡These can never be both true, or O Some Vine is not a Tree. i both false at the same time. If two universals differ in quality they are contraries ; as A Every Vine is a Tree. These can never be both true toge- E No Vine is a Tree. S ther, but they may be both false. * The reader should remember bere, that a proposition according to its quantity is called universal or particular ; and according to its quality is either ejfirmanue or negative.
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