For what man knows the things of a man except the spirit of the man which is in him? Even so no one knows the things of God except the Spirit of God. 12 Now we have received, not the spirit of the world, but the Spirit who is from God, that we might know the things that have been freely given to us by God.
13 These things we also speak, not in words which man’s wisdom teaches but which the Holy Spirit teaches, comparing spiritual things with spiritual. 14 But the natural man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know them, because they are spiritually discerned. 15 But he who is spiritual judges all things, yet he himself is rightly judged by no one. 16 For “who has known the mind of the Lord that he may instruct Him?” But we have the mind of Christ.
— 1 Corinthians 2:11-16.
The Christian has received ‘the Spirit who is from God’ who teaches him both the truth about God and the truth about himself, underlines his need, and intensifies his desire for God’s revelation through His word. The unconverted man (the ‘natural man’) cannot understand these things, because they are spiritually discerned. No one can have God’s mind unless he or she has been converted. The Christian has ‘the mind of Christ’.