39.  A suitable and worthy comprehension and exposition of this subject demands a discussion of greater length than the present occasion, or even our life, as I suppose, allows, and, what is more, both now and at all times, the aid of the Spirit, by Whom alone we are able to perceive, to expound, or to embrace, the truth in regard to God.  For the pure alone can grasp Him Who is pure and of the same disposition as himself; and I have now briefly dwelt upon the subject, to show how difficult it is to discuss such important questions, especially before a large audience, composed of every age and condition, and needing like an instrument of many strings, to be played upon in various ways; or to find any form of words able to edify them all, and illuminate them with the light of knowledge.  For it is not only that there are three sources from which danger springs, understanding, speech, and hearing, so that failure in one, if not in all, is infallibly certain; for either the mind is not illuminated, or the language is feeble, or the hearing, not having been cleansed, fails to comprehend, and accordingly, in one or all respects, the truth must be maimed:  but further, what makes the instruction of those who profess to teach any other subject so easy and acceptable—viz. the piety Piety, εὐλάβεια. i.e. The pious readily and attentively receive instruction in morality or generally received truth, but are more suspicious and intolerant than ordinary people, if, at a time when any theological question is hotly debated, a preacher touches upon any point connected with it, and so stirs party feeling or personal prejudice. of the audience—on this subject involves difficulty and danger.