Having now repelled these objections by the answer which we have given, let us hasten on to the discussion of the subject itself, in which it is said, “It is not of him that willeth, nor of him that runneth, but of God that showeth mercy.”[528] In the book of Psalms—in the songs of Degrees, which are ascribed to Solomon—the following statement occurs: “Except the Lord build the house, they labour in vain that build it; except the Lord keep the city, the watchman waketh but in vain.”[529] By which words he does not indeed indicate that we should cease from building or watching over the safe keeping of that city which is within us; but what he points out is this, that whatever is built without God, and whatever is guarded without Him, is built in vain, and guarded to no purpose. For in all things that are well built and well protected, the Lord is held to be the cause either of the building or of its protection. As if, _e.g._, we were to behold some magnificent structure and mass of splendid building reared with beauteous architectural skill, would we not justly and deservedly say that such was built not by human power, but by divine help and might? And yet from such a statement it will not be meant that the labour and industry of human effort were inactive, and effected nothing at all. Or again, if we were to see some city surrounded by a severe blockade of the enemy, in which threatening engines were brought against the walls, and the place hard pressed by a vallum, and weapons, and fire, and all the instruments of war, by which destruction is prepared, would we not rightly and deservedly say, if the enemy were repelled and put to flight, that the deliverance had been wrought for the liberated city by God? And yet we would not mean, by so speaking, that either the vigilance of the sentinels, or the alertness of the young men,[530] or the protection of the guards, had been wanting. And the apostle also must be understood in a similar manner, because the human will alone is not sufficient to obtain salvation; nor is any mortal running able to win the heavenly [rewards], and to obtain the prize of our high calling[531] of God in Christ Jesus, unless this very good will of ours, and ready purpose, and whatever that diligence within us may be, be aided or furnished with divine help. And therefore most logically[532] did the apostle say, that “it is not of him that willeth, nor of him that runneth, but of God that showeth mercy;” in the same manner as if we were to say of agriculture what is actually written: “I planted, Apollos watered; but God gave the increase. So then neither is he that planteth anything, neither he that watereth; but God that giveth the increase.”[533] As, therefore, when a field has brought good and rich crops to perfect maturity, no one would piously and logically assert that the husbandman had made those fruits, but would acknowledge that they had been produced by God; so also is our own