But if all prophesy - See the note at 1 Corinthians 14:1. If all, in proper order and time, shall utter the truths of religion in a language intelligible to all.
Or one unlearned - One unacquainted with the nature of Christianity, or the truths of the gospel.
He is convinced of all - He will be convinced by all that speak. He will understand what is said; he will see its truth and force, and be will be satisfied of the truth of Christianity. The word here rendered “convinced” (ἐλέγχετἀι elengchetai) is rendered “reprove” in John 16:8, “And when he is come, he will reprove the world of sin,” etc. Its proper meaning is to “convict,” to show one to be wrong; and then to rebuke, reprove, admonish, etc. Here it means, evidently, that the man would be convicted, or convinced of his error and of his sin; he would see that his former opinions and practice had been wrong; he would see and acknowledge the force and truth of the Christian sentiments which should be uttered, and would acknowledge the error of his former opinions and life. The following verse shows that the apostle means something more than a mere convincing of the understanding, or a mere conviction that his opinions had been erroneous. He evidently refers to what is now known also as “conviction” for sin; that is, a deep sense of the depravity of the heart, of the errors and follies of the past life, accompanied with mental anxiety, distress, and alarm. The force of truth, and the appeals which should be made, and the observation of the happy effects of religion, would convince him that he was a sinner, and show him also his need of a Saviour.
He is judged by all - By all that speak; by all that they say. The “effect” of what they say shall be, as it were, to pass a “judgment” on his former life; or to condemn him. What is said will be approved by his own conscience, and will have the effect to condemn him in his own view as a lost sinner. This is now the effect of faithful preaching, to produce deep self-condemnation in the minds of sinners.