The message of the Gospel does not require persuasive words of wisdom (i.e. erudition and practice of the art of oratory) for its transmission.
The Apostle Paul gave that up, simply announcing the crucified Christ (the Messiah). Thus, the faith of those converted was not based on human arguments, but on the power of God, the Holy Spirit, who convinces the sinner of his sin and leads to faith in Christ Jesus.
It is from God, addressed to the perfect, or mature in the faith, and contains the plan of God for the salvation of men since before the centuries (prior to their creation). It is different from the wisdom of men, and the authorities of this world did not to know it, because if they had known they would not have crucified the Lord of glory.
man by himself is unable to comprehend what God has prepared for him. But God has revealed it through His spirit, who knows all things of God.
He is given when we convert to God, and He teaches us, so we can comprehend and understand spiritual things, what is impossible for the natural man.
So Paul could compare spiritual things with spiritual things (for example, compare the realities of the Gospel with figures and prophecies of the Old Testament).
Spiritual man (who is directed and taught by the Holy Spirit), has the mind of Christ, and comes to understand all the things that God reveals to us, but natural man does not understand them.
R David Jones
1 And *I*, when I came to you, brethren, came not in excellency of word, or wisdom, announcing to you the testimony of God.
2 For I did not judge it well to know anything among you save Jesus Christ, and *him* crucified.
3 And *I* was with you in weakness and in fear and in much trembling;
4 and my word and my preaching, not in persuasive words of wisdom, but in demonstration of the Spirit and of power;
5 that your faith might not stand in men's wisdom, but in God's power.
6 But we speak wisdom among the perfect; but wisdom not of this world, nor of the rulers of this world, who come to nought.
7 But we speak God's wisdom in a mystery, that hidden wisdom which God had predetermined before the ages for our glory:
:8 which none of the princes of this age knew, (for had they known, they would not have crucified the Lord of glory;)
9 but according as it is written, Things which eye has not seen, and ear not heard, and which have not come into man's heart, which God has prepared for them that love him,
10 but God has revealed to us by his Spirit; for the Spirit searches all things, even the depths of God.
11 For who of men hath known the things of a man except the spirit of the man which is in him? thus also the things of God knows no one except the Spirit of God.
12 But *we* have received, not the spirit of the world, but the Spirit which is of God, that we may know the things which have been freely given to us of God:
13 which also we speak, not in words taught by human wisdom, but in those taught by the Spirit, communicating spiritual things by spiritual means .
14 But the natural man does not receive the things of the Spirit of God, for they are folly to him; and he cannot know them because they are spiritually discerned;
15 but the spiritual discerns all things, and *he* is discerned of no one.
16 For who has known the mind of the Lord, who shall instruct him? But *we* have the mind of Christ.