[10.] I had desired to enter the lists yet on other difficulties, but perhaps our minds are wearied out; when therefore I have advised you on those points which are useful to us for the hearing, both of what has been said, and of what is yet to be said, I again will hold my peace. What then are these points? I know that many have become confused by reason of the length of what has been spoken. Now this takes place when the soul is heavy laden with many burdens of this life. For as the eye when it is clear and transparent is keen-sighted also, and will not easily be tired in making out even the minutest bodies; but when from some bad humor from the head having poured into it, or some smoke-like fumes having ascended to it from beneath, a kind of thick cloud is formed before the ball, this does not allow it clearly to perceive even any larger object; so is naturally the case with the soul. For when it is purified, and has no passion to disturb it, it looks steadfastly to the fit objects of its regard; but when, darkened by many passions, it loses its proper excellence, then it is not easily able to be sufficient for any high thing, but soon is wearied, and falls back; and turning aside to sleep and sloth, lets pass things that concern it with a view to excellence and the life thence arising, instead of receiving them with much readiness.