The word rendered rude here (idiwthv) means, properly, a private citizen, in opposition to one in a public station; then a plebeian, or one unlettered or unlearned, in opposition to one of more elevated rank, or one who is learned. See Barnes "Ac 4:13"; See Barnes "1 Co 14:16".

The idea is, my language is that of a plain unlettered person. This was doubtless charged upon him by his enemies; and it may be that he designed in part to admit the truth of the charge.

Yet not in knowledge. I do not admit that I am ignorant of the religion which I profess to teach. I claim to be acquainted with the doctrines of Christianity. It does not appear that they charged him with ignorance. If it be asked how the admission that he was rude in speech consists with the fact that he was endowed by the Holy Spirit with the power of speaking languages, we may observe, that Paul had undoubtedly learned to speak Greek in his native place, (Tarsus in Cilicia,) and that the Greek which he had learned there was probably a corrupt kind, such as was spoken in that place. It was this Greek which he probably continued to speak; for there is no more reason to suppose that the Holy Spirit would aid him in speaking a language which he had thus early learned, than he would in speaking Hebrew. The endowments of the Holy Spirit were conferred to enable the apostles to speak languages which they had never learned, not in perfecting them in languages with which they were before acquainted. It may have been true, therefore, that Paul may have spoken some languages which he never learned with more fluency and perfection than he did those which he had learned to speak when he was young. See the remarks of the Archbishop of Cambray, as quoted by Doddridge in loc. It may be remarked, also, that some estimate of the manner of Paul on this point may be formed from his writings. Critics profoundly acquainted with the Greek language remark, that while there is great energy of thought and of diction in the writings of Paul, while he chooses or coins most expressive words, yet that there is everywhere a want of Attic elegance of manner, and of the smoothness and beauty which were so grateful to a Grecian ear.

But we have been throughly made manifest, etc. You have known all about me. I have concealed nothing from you, and you have had ample opportunity to become thoroughly acquainted with me. The meaning is, "I need not dwell on this. I need speak no more of my manner of speech or knowledge. With all that you are well acquainted."

{b} "I be rude" 1 Co 1:17; 2:1,13

{c} "in knowledge" Eph 3:4 {d} "among you" 2 Co 12:12