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 power _one upon another_; which effects are also the signs, by which one taketh notice 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, look in chapter IX.) with the several passions whereof they are signs: _others_ there are which _may_ be _counterfeited_; and those are _words_ or _speech_; of the use and effects 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 one another the same conceptions that we have in ourselves; and this is called _teaching_; wherein, if the _conception_ of him that teacheth continually accompany his words, _beginning_ at something true in _experience_, then it begetteth the like evidence in the hearer that understandeth them, and maketh him to _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’s bare _opinion_. And the _signs_ of two opinions contradictory one to another; namely, _affirmation_ and _negation_ of the same thing, is called _controversy_: but _both affirmations_, or both _negations, consent in opinion_.