In 1 Thessalonians 1:5, Paul acknowledges that the saints received the Gospel, not in word only, but in power and in the Holy Spirit with full conviction. All who hear the proclamation of the Gospel hear the words. That is the outward call to believe in repent. However, only those who hear the inward, powerful, life-giving call of the Holy Spirit are fully convinced that the Gospel is not the words of men but of God.