XIII.  All men, He saith, cannot receive this saying, but they to whom it is given.  When you hear this, It is given, do not understand it in a heretical fashion, and bring in differences of nature, the earthly and the spiritual and the mixed.  For there are people so evilly disposed as to think that some men are of an utterly ruined nature, and some of a nature which is saved, and that others are of such a disposition as their will may lead them to, either to the better, or to the worse.  For that men may have a certain aptitude, one more, another less, I too admit; but not that this aptitude alone suffices for perfection, but that it is reason which calls this out, that nature may proceed to action, just as fire is produced when a flint is struck with iron.  When you hear To whom it is given, add, And it is given to those who are called and to those who incline that way.  For when you hear, Not of him that willeth, nor of him that runneth, but of God that sheweth mercy, Rom. ix. 16. I counsel you to think the same.  For since there are some who are so proud of their successes that they attribute all to themselves and nothing to Him that made them and gave them wisdom and supplied them with good; such are taught by this word that even to wish well needs help from God; or rather that even to choose what is right is divine and a gift of the mercy of God.  For it is necessary both that we should be our own masters and also that our salvation should be of God.  This is why He saith not of him that willeth; that is, not of him that willeth only, nor of him that runneth only, but also of God.  That sheweth mercy.  Next; since to will also is from God, he has attributed the whole to God with reason.  However much you may run, however much you may wrestle, yet you need one to give the crown.  Except the Lord build the house, they laboured in vain that built it:  Except the Lord keep the city, in vain they watched that keep it. Ps. cxxvii. 1.  I know, He says, that the race is not to the swift, nor the battle to the strong, Eccles. ix. 11. nor the victory to the fighters, nor the harbours to the good sailors; but to God it belongs both to work victory, and to bring the barque safe to port.