What good is purity of speech if it does not lead to understanding in the hearer? There is no use at all in speaking if the people we are speaking for do not understand us. Whoever teaches, therefore, will avoid all words that do not teach. And if instead of them he can find words that are both pure and intelligible, he will pick those first. If, however, he cannot, either because there are no such words, or because they do not at the time occur to him, he will use words that are not quite pure, as long as the meaning of his thought is conveyed and understood in its integrity.