The phrase διʼ ἀποκαλύψεως Ἰησοῦ Χριστοῦ (literally, "through a revelation of Jesus Christ") is the positive, theologically powerful assertion of how Paul did indeed receive his gospel. The Greek word ἀποκάλυψις bears the most weight in the phrase. It commonly meant “revelation, disclosure,” and here the sense of the word does not deviate from that common meaning. But the referent of the entire expression is key, which leads to a discussion of the genitive Ἰησοῦ Χριστοῦ. The usual debate is whether this is a subjective genitive (“the revelation which Jesus Christ made [of himself]”) or an objective genitive (“the revelation about Jesus Christ”). The emphasis in the context of the divine origin of Paul’s gospel could lead to the subjective genitive, but the preposition διά plus the genitive here indicates intermediate agency; as his subsequent discussion in 1:15-16 will show, there was someone at work communicating to Paul through this revelation, and it would be awkward for Christ to be viewed as the ultimate agent and the subject of the genitive at the same time. Two other data are helpful here: When Paul uses the cognate verb ἀποκαλύπτω in the active voice, thus expressing the subject as the ultimate agent of the verb, explicity it is God twice (1 Cor 2:10; Phil 3:15) and implicitly once (Gal 1:16, where I take the shorter reading as original). He also uses the phrase ἀποκάλυψις κυρίου [Ἰησοῦ] twice (1 Cor 1:7; 2 Thess 1:7), and each time it has to be an objective genitive, because it refers to Christ's appearing at the parousia. Thus the phrase διʼ ἀποκαλύψεως Ἰησοῦ Χριστοῦ most likely means “by means of / through a disclosure about Jesus Christ.” This does not mean a mystical revelation of knowledge, but instead a disclosure from God which has as its object Jesus Christ. The referent of this revelation must be Paul’s conversion, which fundamentally changed his understanding about who Jesus was and his attitude towards him. So at the same time Paul can literally refer to the tangible revelation of Christ to him on the road to Damascus, but also to the revelation of new understanding about him which came from that appearance. More importantly, we need not miss the bigger point Paul makes: God has done something new to reveal Jesus Christ to him, and thus logically God is powerfully at work in Paul’s present proclamation of the gospel, as he was the origin of its transmission to him.