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COMMENT.
IT is absolutely necessary, that a Man who makes any pretensions to Philosophy, and aims at the peculiar perfection of his Nature, both as he is an Animal, and a Rational Crea∣ture, should have a clear and demonstrative know∣ledge of the Truth: For otherwise, he may be liable to great Errors, and run into infinite Incon∣veniences, by taking things upon trust, and lean∣ing too much either to the bare Authority, or the insufficient proofs of confident Pretenders. Ver∣tue is a thing of the highest Consequence, and it is not fit we should take up with so slight and fee∣ble Perswasions concerning it, as mere Opinion and Probabilities are capable of creating in us. Now this clear and undoubted Evidence is an ef∣fect owing only to Demonstration. And it is Logick's peculiar Province, to inform us in the Nature of a Demonstration, as, That it is a Syl∣logism consisting of Propositions, put together according to Rules of Art; and that those Pro∣positions must be of clear and undoubted Truth: As also to acquaint us what Propositions are thus qualified, and what Method is to be observed for the forming them into a true Syllogism.
Now from hence we may plainly perceive, that the whole compass of Philosophy may be reduced to three Heads, and that these will comprehend if not all absolutely, yet all that is material and necessary in it. The First is the Preceptive part, that which converts our Speculation into Practice, that prescribes Modesty and Temperance in our Actions, and prohibits lying in all our Discourse and Conver∣sation.