Called to be an apostle (klhto apostolo). Verbal adjective klhto from kalew, without einai, to be. Literally, a called apostle ( Romans 1:1 ), not so-called, but one whose apostleship is due not to himself or to men ( Galatians 1:1 ), but to God, through the will of God (dia qelhmato tou qeou). The intermediate (dia, duo, two) agent between Paul's not being Christ's apostle and becoming one was God's will (qelhma, something willed of God), God's command ( 1 Timothy 1:1 ). Paul knows that he is not one of the twelve apostles, but he is on a par with them because, like them, he is chosen by God. He is an apostle of Jesus Christ or Christ Jesus (MSS. vary here, later epistles usually Christ Jesus). The refusal of the Judaizers to recognize Paul as equal to the twelve made him the more careful to claim his position. Bengel sees here Paul's denial of mere human authority in his position and also of personal merit: Namque mentione Dei excluditur auctoramentum humanum, mentione Voluntatis Dei, meritum Pauli. Our brother (o adelpo). Literally, the brother, but regular Greek idiom for our brother. This Sosthenes, now with Paul in Ephesus, is probably the same Sosthenes who received the beating meant for Paul in Corinth ( Acts 18:17 ). If so, the beating did him good for he is now a follower of Christ. He is in no sense a co-author of the Epistle, but merely associated with Paul because they knew him in Corinth. He may have been compelled by the Jews to leave Corinth when he, a ruler of the synagogue, became a Christian. See 1 Thessalonians 1:1 for the mention of Silas and Timothy in the salutation. Sosthenes could have been Paul's amanuensis for this letter, but there is no proof of it.