92 LOGIC : OR, THE RIGHT'vaE OF REASON. I grant there may be good use of this practice for persons of a lower genius, when they are to compose any. discourse for the public ; or for those of superior parts, to refresh their me- mory, and revive their acquaintance with a subject which has been long absent from their thoughts, or when their natural spi- rits labour under indisposition and languor : but when a man of moderate sagacity, has made himself master of his theme by just diligence and enquiry, he has seldom need to run knocking at the doors of all the topics that he may furnish himself with argument or matter of speaking : And indeed it is only a man of sente and judgment that can use common places or topics well ; for amongst this variety he only knows what is fit to he left -out, as well as what is fit to be spoken. By some logical writers this business of topics and invention is treated of in such a manner with mathematical figures and diagrams, filled with the barbarous technical words, Napeas, Nipeis, Ropcos, Nosrop, ACc. as though an ignorant lad were to . he led mechanically in certain artificial harnasses and trammels to find out arguments to prove or refute any proposition whatso- ever, without any rational knowledge of the ideas. Now there is no need to throw words of contempt on such a practice : the very description of it carries reproof and ridicule in abundance. SECT. VIIIï Of several Kinds of Arguments and Demon- strations. WE proceed now to the division of syllogisms according to the middle term; and in this part of our treatise the syllogisnis themselves are properly called arguments, and are thus distri- buted. I. Arguments are called grammatical, logical, metaphysi- cal, physical, moral, mechanical, theological, &c. according to the art, science, or subject, whence the middle term or topic is borrowed. Thus, if we prove that no man shall steal from his neighbour, because the scripture forbids it, this is a theological argument : if we prove it from the laws of the land, it is poli- tical : but if we prove it from the principles of reason and equity the argument is moral. II. Arguments art either certain and evident, or doubtful and merely probable. Probable arguments are those whose conclusions are proved by some probable medium ; as, This hill was once a church -yard, or a field of battle, because there are many human bones found here. This is not a certain argument, for human bones might have been conveyed there some other way. Evident and certain arguments are called demonstrations ; for they prove their conclusions by clear mediums and undoubted principles ; and they are generally divided into these two sorts :
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