If does not mean that Paul has any doubt. The Greek may be translated as “Since I must boast” or “Since I have to lift myself up [or, show myself].” Or it may be possible to translate “If I am forced to boast…” or “Whenever I have to boast….”

The future tense I will boast does not mean that Paul only now will begin to boast, but that he plans to boast in the following manner. What follows in this verse is a summary statement of the kinds of things that he plans to boast about whenever he must.

My weakness: the term used here is found in Rom 8.26 and 1 Cor 2.3. It occurs again in this letter at 12.9 and 13.4. In some languages it may be more naturally translated by a verbal expression such as “that I lack strength.”

Quoted with permission from Omanson, Roger L. and Ellingworth, Paul. A Handbook on Paul’s Second Letter to the Corinthians. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .