Paul began this letter by defending his apostleship and he closes his letter by demonstrating his apostleship. He does so by admitting his weakness (large letters/poor eyesight) instead of emphasizing his strengths; his willingness to be persecuted instead of avoiding it through compromise; through the crucifixion of the world to him (rejecting the world's values) and him to the world (being rejected by man). Following the law is nothing, being transformed by the gospel is everything. The one who bore the marks of Jesus in his body can be trusted as a true apostle and therefore, communicator of divine truth that we can base our lives upon.