1CO 2:14 But a natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised.
1CO 2:15 But he who is spiritual appraises all things, yet he himself is appraised by no one.
The things of God are beyond a man who is not in the right spiritual condition. An unsaved man (the natural man in verse 14) who is not aided by the Holy Spirit is like a blind man, who never saw the light of day since birth, attending a lecture about the colors of the rainbow. They have no value to him. In order to appreciate it, his eyes must be opened.
In the same way, in order to spiritually appraise, that is, in order to realize the value of the things of God, one must be spiritual or one must be aided by the Holy Spirit. Through the aid of the Holy Spirit he is able to discern and realize their worth.
This, in turn, affects his perspective and outlook in life. He marches through life to the sound of a different drumbeat. And the natural men around him find him an enigma and a puzzle. They don't understand him since he is out of step with them. They find him foolish since no one among them can truly appraise him and therefore understand him.
