2 Corinthians 11:6

‘But if it be that I am rude in speech, yet am I not in knowledge; no, in every way have we made this openly clear to you in all things.'

His opponents are accusing him of not preaching like a trained orator. Well, he will not agree with their verdict, but even if it were true it is his deliberate policy not to flaunt himself and not to hide the truth with flowery words (1 Corinthians 2:1). Nevertheless that says nothing about what he knows, about the knowledge that he possesses. He certainly is not ‘rude' (lacking as an amateur, as a layman) in knowledge. He has fullness of knowledge, as the Twelve do. He knows the ‘full knowledge of the glory of God in the face of Jesus Christ' (2 Corinthians 4:6). And indeed he and his co-workers have made all the knowledge that they have openly clear in every way. They do not hide it behind verbosity or superiority.