Here the Prophet explains more clearly what would otherwise be obscure. He says that the living creatures ran, and returned like lightning: by which words he doubtless signifies their amazing swiftness. For lightning (as Christ uses that comparison when he speaks of his own Advent -- Matthew 24:27) goes forth from one part of the world and penetrates instantly to the opposite. Since, then, the swiftness of lightning is so great that it reaches in a moment through the immensity of heaven, for this reason the Prophet says, the living creatures ran, and returned like lightning: as if he had said, in whatever direction God wishes to impel them, they were ready to obey; as we have formerly said, angels are at hand to obey the commands of God: but we cannot comprehend the extreme swiftness of their course, unless by this comparison of lightning. Now we see how well these two things agree, that they did return and yet did not: they did not return until they had arrived, as I have already said, at the goal, because, although many hindrances occur, yet God breaks through them, so that they never interrupt his actions. The devil, indeed, by his obstacles, endeavors to compel God to recede; but here the Prophet shows that when God determines anything, the angels are ready to govern the world, and that they have so much vigor in them, that they go on constantly to the end, as far as God inspires them with his own power. Afterwards it follows --