The Vigil of Pentecost.
A Homily by Augustine the Bishop
The Evangelist saith, concerning the Spirit of Truth, that the world cannot receive him, because it seeth him not, neither knoweth him. For to love the world is to lack those spiritual eyes, which are able to see him who is invisible, namely, the Holy Ghost. But, saith the Lord to his disciples : Ye know him, for he dwelleth with you, and shall be in you abidingly. The Lord did not mean that the Spirit would come to dwell for a while, and so be in his people only for a season. According to this latter sense of the verb To Be, one must first be in a place before one can dwell there. So, lest the Apostles should think that the words : He shall dwell with you : signified that he should visibly abide with them for a while as guests in the houses of men, the Lord added in explanation : He shall be in you : which is to say : He shall abide in you.
On this wise, then, is he seen that is invisible : If he were not in us we could have in us no knowledge of him ; but he is seen in us, as we see our consciences. We see the faces of other men, and we cannot see our own ; but of men’s consciences we see none save that which is within ourselves. However, our conscience is never elsewhere except within us ; whereas the Holy Ghost may be outside of us, as well as within us. He is given to be within us, and unless he is within us, we can neither see nor know him, either within us or outside us. Then, after the Lord had promised the Holy Ghost, (lest anyone should fancy that he intended to give them this Comforter in place of himself, and he himself was to be no longer with them, but leave them as orphans, ) he said also : I will not leave you comfortless ; I will come to you. Therefore, although the Son of God hath made us by adoption sons of his own Father, and hath willed that the Same who is his Father by nature should e our Father by grace, nevertheless, he sheweth that he himself hath towards us a love as of a father, whereof he saith : I will not leave your comfortless, that is , orphans.