1 Corinthians 2:10

But God hath revealed them unto us by His Spirit. S. Paul here anticipates an objection. It might be said, "If eye hath not seen, neither have entered into the heart of man, the wisdom and the glory that Christ has prepared for His friends, how is it that you boast yourself of its possession?" Paul replies that he knows them not by sight, sensation, or by the understanding, but by the inspiration and revelation of God. Hence, Clement of Alexandria (Pædag. lib. i. c. 6) interprets the phrase, "ear hath not heard," by adding, "except that ear which was taken up into the third heaven," viz., Paul's, who heard with the ear in Paradise mystic words which it is not lawful for a man to utter. Paul means, then, that God has revealed these things to us His Apostles and Prophets filled with His Spirit, in order that we may teach you and others. It appears from this that not only is our longing for bliss and glory supernatural, but that our knowledge of them is also, whether that knowledge be of them in their essence, or merely the obscure and fragmentary knowledge of the Apostles and of all others who are still "in the way." Consequently there is not naturally in man any perfect and effectual desire, or appetite, for this bliss.

The Spirit searcheth all things, the deep things of God. That is, penetrates into and perceives everything. For when men want to learn something of which they are ignorant, they are wont to search and inquire about it. But God, without any such searching, knows everything at a glance, and as it were by a single application of His mind. (S. Thomas, Theodoret, Theophylact.)

The deep things of God are all the most secret and inward counsels of God. Amongst them the chiefest is this mystery of man's glory and redemption by Christ. All these the Holy Spirit penetrates into and clearly views, because He is of one essence and knowledge with God, and therefore He so "searches the deep things of God," that nothing in God remains unknown t Him. His knowledge and sight equal their object, and He knows God as he can be known; i.e., the Holy Spirit, because He is God, comprehends God and His Divinity as completely as He comprehends Himself. (Molina part i. qu. 14, a. 3, Theodoret, S. Thomas.) From this passage Ambrose and other Fathers prove the Godhead of the Holy Ghost against the Macedonians. To sum up S. Paul's meaning: The Holy Spirit has revealed to us these mysteries and secrets of God: He knows all the secrets of God, and therefore He searches and clearly views the deep things of God.