NET

12 For our reason for confidence is this: the testimony of our conscience, that with pure motives and sincerity which are from God—not by human wisdom but by the grace of God—we conducted ourselves in the world, and all the more toward you.

Darby

12 For our boasting is this, the testimony of our conscience, that in simplicity and sincerity before God, (not in fleshly wisdom but in God's grace,) we have had our conversation in the world, and more abundantly towards you.

KJV

12 For our rejoicing is this, the testimony of our conscience, that in simplicity and godly sincerity, not with fleshly wisdom, but by the grace of God, we have had our conversation in the world, and more abundantly to you-ward.