4 But when He says, “I will ask the Father, and He shall give you another Paraclete,” He intimates that He Himself is also a paraclete. For paraclete is in Latin called advocatus (advocate); and it is said of Christ, “We have an advocate with the Father, Jesus Christ the righteous.” But He said that the world could not receive the Holy Spirit, in much the same sense as it is also said, “The minding of the flesh is enmity against God: for it is not subject to the law of God; neither indeed can be;” just as if we were to say, Unrighteousness cannot be righteous. For in speaking in this passage of the world, He refers to those who love the world; and such a love is not of the Father. And thus the love of this world, which gives us enough to do to weaken and destroy its power within us, is in direct opposition to the love of God, which is shed abroad in our hearts by the Holy Spirit who is given unto us. “The world,” therefore, “cannot receive Him, cause it sees Him not, neither knows Him.” For worldly love possesses not those invisible eyes, whereby, save in an invisible way, the Holy Spirit cannot be seen.
Source: Tractates on the Gospel of John (New Advent)