en_tn/2co/11/06.md

I am not untrained in knowledge

This negative phrase emphasizes the positive truth that he is trained in knowledge. The abstract noun "knowledge" can be translated with a verbal phrase. AT: "I am certainly trained in knowledge" or "I am trained to know what they know" (See: rc://en/ta/man/translate/figs-litotes and rc://en/ta/man/translate/figs-abstractnouns)