Infallibility?

Q. 1 Corinthians 2:15 But he that is spiritual judges all things, yet he himself is judged of no man. What does “judged of no man” mean? Is seems to be talking about the infallibility of clergy or the Catholic theory. It does not make any sense with Acts 17:11 Now the Berean Jews were of more noble character than those in Thessalonica, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true.

A. It is not talking about infallibility. The word “infallible” appears only once in the Bible:
• Acts 1:3 to whom He also presented Himself alive after His suffering by many infallible proofs, being seen by them during forty days and speaking of the things pertaining to the kingdom of God. (NKJV)

It means:
• that from which something is surely and plainly known,
• on unquestionable evidence, impossible to doubt.

Only God and His word are infallible in the sense of “incapable of being wrong, unable to err”. Paul knew he was a sinner, and even claimed to be chief:
• 1 Tim 1:15 It is a trustworthy statement, deserving full acceptance, that Christ Jesus came into the world to save sinners, among whom I am foremost of all.
By definition sinners are wrong and cannot be infallible. For any human to claim infallibility is foolishness.

As always, the meaning is determined by the context. The whole chapter 2 of 1 Co is talking about Paul’s reliance on the Spirit. In particular, the immediate context is 1 Co 2:14-16 (NASB):
• 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.
• 15 But he who is spiritual appraises all things, yet he himself is appraised by no one.
• 16 For WHO HAS KNOWN THE MIND OF THE LORD, THAT HE WILL INSTRUCT HIM? But we have the mind of Christ.

The natural man, the man who does not know God cannot understand spiritual things, because they must be spiritually evaluated or discerned with the mind of Christ. A spiritual person, one who is controlled by the Spirit, is able to judge all things, yet no one (the unbeliever) can understand him.

Let me quote from a few paraphrases to make it clearer:
• AMPLIFIED BIBLE But the spiritual man [the spiritually mature Christian] judges all things [questions, examines and applies what the Holy Spirit reveals], yet is himself judged by no one [the unbeliever cannot judge and understand the believer’s spiritual nature].
• THE MESSAGE The unspiritual self, just as it is by nature, can’t receive the gifts of God’s Spirit. There’s no capacity for them. They seem like so much silliness. Spirit can be known only by spirit—God’s Spirit and our spirits in open communion. Spiritually alive, we have access to everything God’s Spirit is doing, and can’t be judged by unspiritual critics.
• PHILLIP’S NT But the unspiritual man simply cannot accept the matters which the Spirit deals with—they just don’t make sense to him, for, after all, you must be spiritual to see spiritual things. The spiritual man, on the other hand, has an insight into the meaning of everything, though his insight may baffle the man of the world.

Hope this helps.