The Vigil of Pentecost: Homily by S. Augustine, Bishop: Homily 74 on John

IN saying, I will pray the Father, and he shall give you another Paraclete, he shews that he is himself a Paraclete. And indeed, Paraclete is in our tongue, Advocate: and it is said of Christ, we have an advocate with the Father, Jesus Christ the righteous. And that the world cannot receive the Holy Spirit he said in the same regard as it is said, the wisdom of the flesh is at enmity with God: for to the law of God it is not subject, neither indeed can be: just as if we should say, Unrighteousness cannot be righteous. In fact, by World, in this place he means lovers of the world, which love is not of the Father. And therefore, to the love of this world (which it is our business to get diminished and consumed away in us) the love of God is contrary, which love is shed abroad in our hearts by the Holy Spirit which is given to us.

THE world then cannot receive him, because it seeth him not, neither knoweth him. For worldly love hath not the invisible eyes by which the Holy Spirit can only be invisibly beheld. But, saith he, ye shall know him, because he shall dwell with you, and shall be in you. Shall be in them that he may dwell, not dwell that he may be: for to be somewhere comes before dwelling. Only, lest they should think the saying, shall dwelt with you, to be spoken in the customary sense of a guest visibly dwelling with a man, he expounded what he meant by, Shall dwell with you, when he further said, Shall be in you. Therefore he is invisibly seen :  nor, if he be not in us, can the knowledge of him be in us. For in this way is our own conscience seen by us in ourselves: we see another's face, our own we cannot see. Our conscience we see, another's we see not. But then, conscience never is anywhere but in us, whereas the Holy Spirit can also be without us, as in fact he is given to be also in us. But seen and known as he ought to be seen and known, by us he cannot be, if he be not in us.

AFTER making promise or the Holy Ghost, lest any should imagine that the Lord meant to give him as though instead of himself, so that he should not also himself be with them, he went on to say, I will not leave you orphans; I will come to you. Albeit therefore the Son of God hath adopted us to be sons to his Father, and willed us to have the same to be our Father by grace which is his by nature, yet even he in some sort sheweth toward us a fatherly affection, when he saith, I will not leave you orphans, I will come to you.