1. Having spoken of the powers and acts of the mind, both cognitive and motive, considered in every man by himself, without relation to others; it will fall fitly into this chapter, to speak of the effects of the same powers one upon another; which effects are also the signs, by which one taketh notice of what another conceiveth and intendeth. Of these signs, some are such as cannot easily be counterfeited; as actions and gestures, especially if they be sudden; whereof I have mentioned some for example sake in the ninth chapter, at the several passions whereof they are signs; others there are that may be counterfeited: and those are words or speech; of the use and effect whereof I am to speak in this place.
2. The first use of language, is the expression of our conceptions, that is, the begetting in another the same conceptions that we have in ourselves; and this is called TEACHING; wherein if the conceptions of him that teacheth continually accompany his words, beginning at something from experience, then it begetteth the like evidence in the hearer that understandeth them, and maketh him know something, which he is therefore said to LEARN. But if there be not such evidence, then such teaching is called PERSUASION, and begetteth no more in the hearer, than what is in the speaker, bare opinion. And the signs of two opinions contradictory one to another, namely' affirmation and negation of the same thing, is called a CONTROVERSY; but both affirmations, or both negations, CONSENT in opinion.
3. The infallible sign of teaching exactly, and without error, is this: that no man hath ever taught the contrary; not that few, how few soever, if any. For commonly truth is on the side of the few, rather than of the multitude; but when in opinions and questions considered and discussed by many, it happeneth that not any one of the men that so discuss them differ from another, then it may be justly inferred, they know what they teach, and that otherwise they do not. And this appeareth most manifestly to them that have considered the divers subjects wherein men have exercised their pens, and the divers ways in which they have proceeded; together with the diversity of the success thereof. For those men who have taken in hand to consider nothing else but the comparison of magnitudes, numbers, times, and motions, and their proportions one to another, have thereby been the authors of all those excellences, wherein we differ from such savage people as are now the inhabitants of divers places in America; and as have been the inhabitants heretofore of those countries where at this day arts and sciences do most flourish.
