6. Hence then cometh the groaning of the Spirit of God, and those groans of the Prophet[184], truly unutterable because they are divine. So those words which Paul heard in heaven are _unspeakable, which it is not lawful for a man to utter_, but what is hidden from man is known to God. Now He Who is the Searcher of hearts knows all things, but the things which He searches are those which the Spirit hath cleansed. God therefore knoweth what the Spirit prays for, and what is the wisdom of the Spirit Which intercedes for the saints, as it is written, _For the Spirit maketh intercession for us_. For those for whom Christ suffered, and whom He cleansed by His Blood, for them the Spirit also intercedes. Farewell: love me as a Son, for I too love you. LETTER XXXVII. A.D. 387. SIMPLICIAN, to whom this and the following Letters, and several later ones, are addressed, seems, from what little we know of him, to have been a very learned and yet simple-minded man. He was older than S. Ambrose, who speaks in this Letter of his ‘fatherly love’ towards himself, and was probably his adviser in the early days of his episcopate, and possibly, as the Benedictine Editors, (note on Letter lxv,) suggest, his ‘father in the faith,’ as having prepared him for his ordination, or even taught him as a catechumen at Rome in earlier days. Paulinus tells us that when S. Ambrose was on his death-bed he overheard some of his Clergy discussing the probabilities as to his successor, and when they mentioned Simplician’s name, he said “as if he were taking part in the convention, ‘Trahitur autem sapientia de occultis.’” Certainly Simplician was unanimously chosen his successor. In this Letter he dwells in detail upon the theme that goodness is true freedom and sin slavery, which he illustrates at great length and with much rarity of argument. It is one of the most interesting of his expository Letters. AMBROSE TO SIMPLICIAN, GREETING 1. WHEN we were lately conversing together, in the intimacy of an old-standing affection, you let me see that you were much pleased by my taking a passage from the writings of the Apostle Paul to preach upon to the people. You said further that this was the case, because the depth of his counsels is difficult to grasp, while the loftiness of his sentiment rouses the audience, and stimulates the preacher; and also because his discourses are so fully, for the most part, the interpreters of his meaning, that the expounder of them finds nothing to add of his own, and, if he would say ought, fills the part of a critic rather than of a preacher.