Today is the feast of St. Augustine of Hippo, Bishop and Doctor of the Church. From Tractate 97 on the Gospel of John:
The Holy Spirit, whom the Lord promised to send to His disciples, to teach them all the truth which, at the time He was speaking to them, they were unable to bear: of the which Holy Spirit, as the apostle says, we have now received the earnest, an expression whereby we are to understand that His fullness is reserved for us till another life: that Holy Spirit, therefore, teaches believers also in the present life, as far as they can severally apprehend what is spiritual; and enkindles a growing desire in their breasts, according as each one makes progress in that love, which will lead him both to love what he knows already, and to long after what still remains to be known: so that those very things which he has some notion of at present, he may know that he is still ignorant of, as they are yet to be known in that life which eye has not seen, nor ear heard, nor the heart of man has perceived. But were the inner Master wishing at present to say those things in such a way of knowing, that is, to unfold and make them patent to our mind, our human weakness would be unable to bear them. Whereof you remember, beloved, that I have already spoken, when we were occupied with the words of the holy Gospel, where the Lord says, I have yet many things to say unto you, but you cannot bear them now. Not that in these words of the Lord we should be suspecting an over-fastidious concealment of no one knows what secrets, which might be uttered by the Teacher, but could not be borne by the learner, but those very things which in connection with religious doctrine we read and write, hear and speak of, as within the knowledge of such and such persons, were Christ willing to utter to us in the self-same way as He speaks of them to the holy angels, in His own Person as the only-begotten Word of the Father, and co-eternal with Him, where are the human beings that could bear them, even were they already spiritual, as the apostles still were not when the Lord so spoke to them, and as they afterwards became when the Holy Spirit descended? For, of course, whatever may be known of the creature, is less than the Creator Himself, who is the supreme and true and unchangeable God.
