Chapter 25.—Four Moral Duties Regarding the Love of God, of Which Love the Reward is Eternal Life and the Knowledge of the Truth. 46.  I need say no more about right conduct.  For if God is man’s chief good, which you cannot deny, it clearly follows, since to seek the chief good is to live well, that to live well is nothing else but to love God with all the heart, with all the soul, with all the mind; and, as arising from this, that this love must be preserved entire and incorrupt, which is the part of temperance; that it give way before no troubles, which is the part of fortitude; that it serve no other, which is the part of justice; that it be watchful in its inspection of things lest craft or fraud steal in, which is the part of prudence.  This is the one perfection of man, by which alone he can succeed in attaining to the purity of truth.  This both Testaments enjoin in concert; this is commended on both sides alike.  Why do you continue to cast reproaches on Scriptures of which you are ignorant?  Do you not see the folly of your attack upon books which only those who do not understand them find fault with, and which only those who find fault fail in understanding?  For neither can an enemy know them, nor can one who knows them be other than a friend to them. 47.  Let us then, as many as have in view to reach eternal life, love God with all the heart, with all the soul, with all the mind.  For eternal life contains the whole reward in the promise of which we rejoice; nor can the reward precede desert, nor be given to a man before he is worthy of it.  What can be more unjust than this, and what is more just than God?  We should not then demand the reward before we deserve to get it.  Here, perhaps, it is not out of place to ask what is eternal life; or rather let us hear the Bestower of it:  "This," He says, "is life eternal, that they should know Thee, the true God, and Jesus Christ whom Thou hast sent." 125   So eternal life is the knowledge of the truth.  See, then, how perverse and preposterous is the character of those who think that their teaching of the knowledge of God will make us perfect, when this is the reward of those already perfect!  What else, then, have we to do but first to love with full affection Him whom we desire to know? 126   Hence arises that principle on which we have all along insisted, that there is nothing more wholesome in the Catholic Church than using authority 127 before argument. 125     John xvii. 3 . 126     Retract . i. 7. § 4:—"I should have said sincere affection rather than full; or it might be thought that the love of God will be no greater when we shall see Him face to face.  Full, then, must be here understood as meaning that it cannot be greater while we walk by faith.  There will be greater, yea, perfect fullness, but only by sight." 127     [By authority Augustin does not mean the authority of the Church or of Scripture, but he refers to the loving recognition of the authority of God as the condition of true discipleship.—A.H.N.]