45. With equal brevity we must treat of prudence, to which it belongs to discern between what is to be desired and what to be shunned. Without this, nothing can be done of what we have already spoken of. It is the part of prudence to keep watch with most anxious vigilance, lest any evil influence should stealthily creep in upon us. Thus the Lord often exclaims, "Watch;" and He says, "Walk while ye have the light, lest darkness come upon you." And then it is said, "Know ye not that a little leaven leaveneth the whole lump?" And no passage can be quoted from the Old Testament more expressly condemning this mental somnolence, which makes us insensible to destruction advancing on us step by step, than those words of the prophet, "He who despiseth small things shall fall by degrees." On this topic I might discourse at length did our haste allow of it. And did our present task demand it, we might perhaps prove the depth of these mysteries, by making a mock of which profane men in their perfect ignorance fall, not certainly by degrees, but with a headlong overthrow.