17 What discourses or writings of philosophers, what laws of any commonwealth in any land or age, are worthy for a moment to be compared with the two commandments on which Christ says that all the law and the prophets hang: “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and you shall love your neighbour as yourself”? All philosophy is here—physics, ethics, logic: the first, because in God the Creator are all the causes of all existences in nature; the second, because a good and honest life is not produced in any other way than by loving, in the manner in which they should be loved, the proper objects of our love, namely, God and our neighbour; and the third, because God alone is the Truth and the Light of the rational soul. Here also is security for the welfare and renown of a commonwealth; for no state is perfectly established and preserved otherwise than on the foundation and by the bond of faith and of firm concord, when the highest and truest common good, namely, God, is loved by all, and men love each other in Him without dissimulation, because they love one another for His sake from whom they cannot disguise the real character of their love.
18. Consider, moreover, the style in which Sacred Scripture is composed—how accessible it is to all men, though its deeper mysteries are penetrable to very few. The plain truths which it contains it declares in the artless language of familiar friendship to the hearts both of the unlearned and of the learned; but even the truths which it veils in symbols it does not set forth in stiff and stately sentences, which a mind somewhat sluggish and uneducated might shrink from approaching, as a poor man shrinks from the presence of the rich; but, by the condescension of its style, it invites all not only to be fed with the truth which is plain, but also to be exercised by the truth which is concealed, having both in its simple and in its obscure portions the same truth. Lest what is easily understood should beget satiety in the reader, the same truth being in another place more obscurely expressed becomes again desired, and, being desired, is somehow invested with a new attractiveness, and thus is received with pleasure into the heart. By these means wayward minds are corrected, weak minds are nourished, and strong minds are filled with pleasure, in such a way as is profitable to all. This doctrine has no enemy but the man who, being in error, is ignorant of its incomparable usefulness, or, being spiritually diseased, is averse to its healing power.
19. You see what a long letter I have written. If, therefore, anything perplexes you, and you regard it of sufficient importance to be discussed between us, let not yourself be straitened by keeping within the bounds of ordinary letters; for you know as well as any one what long letters the ancients wrote when they were treating of any subject which they were not able briefly to explain. And even if the custom of authors in other departments of literature had been different, the authority of Christian writers, whose example has a worthier claim upon our imitation, might be set before us. Observe, therefore, the length of the apostolic epistles, and of the commentaries written on these divine oracles, and do not hesitate either to ask many questions if you have many difficulties, or to handle more fully the questions which you propound, in order that, in so far as it can be achieved with such abilities as we possess, there may remain no cloud of doubt to obscure the light of truth.
20. For I am aware that your Excellency has to encounter the most determined opposition from certain persons, who think, or would have others think, that Christian doctrine is incompatible with the welfare of the commonwealth, because they wish to see the commonwealth established not by the steadfast practice of virtue, but by granting impunity to vice. But with God the crimes in which many are banded together do not pass unavenged, as is often the case with a king, or any other magistrate who is only a man. Moreover, His mercy and grace, published to men by Christ, who is Himself man, and imparted to man by the same Christ, who is also God and the Son of God, never fail those who live by faith in Him and piously worship Him, in adversity patiently and bravely bearing the trials of this life, in prosperity using with self-control and with compassion for others the good things of this life; destined to receive, for faithfulness in both conditions, an eternal recompense in that divine and heavenly city in which there shall be no longer calamity to be painfully endured, nor inordinate desire to be with laborious care controlled, where our only work shall be to preserve, without any difficulty and with perfect liberty, our love to God and to our neighbour.
May the infinitely compassionate omnipotence of God preserve you in safety and increase your happiness, my noble and distinguished Lord, and my most excellent son. With profound respect, as is due to your worth, I salute your pious and most truly venerable mother, whose prayers on your behalf may God hear! My pious brother and fellow bishop, Possidius, warmly salutes your Grace.
Source: Letters (New Advent)