ESV - 48 And when the Gentiles heard this, they began rejoicing and glorifying the word of the Lord, and as many as were appointed to eternal life believed.
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I can see why you think that way, and I'm not going to give you a clear answer. However, I'll give you context. When Paul and Barnabas was preaching in Antioch, there were both Jews and Gentiles living in the city. God had promised that the Jews were promised the kingdom of God. However, it was the Jews that ending up missing Christ because of their way of thinking. Their whole perspective was shifted when Jesus walked on this planet, which was different then what they thought God was going to be like. So the Gentiles were added into God's promise. But what are the Gentiles? The Believers of Christ. That's why you get "many are called, but few are chosen." because God, with his perfect foreknowledge, knew the outcome of your choice of whether to respond to His word. So do we really have a choice? Man thinks that God made the choice for us but God thinks that Man makes the choice. But who ultimately makes the choice is not clear.