is up at The Catholic Weekly:
To be sure, there are those who painstakingly make their way to belief in one God via the route of philosophical argument.
Indeed, we meet some of these people in the pages of the New Testament, where they are known by the technical title of ‘God-fearer’ (cf. Acts 10:2; 22; 13:16; 26).
These were formerly polytheistic Gentiles who had come to believe in the one God of Israel and who were in various stages of seeking initiation to Judaism.
Many of them (Luke is likely one) then became convinced that Jesus was the Messiah Israel had been awaiting and went on to become some of the earliest Christians.
Others, like the Philippian Jailer (Acts 16:25-40), may have come to monotheism, not by believing first in the one God through the witness of Jews, but by coming to belief in Jesus and then, through him, to belief in God the Father.
And some, like C.S. Lewis, come to a purely rational conviction in the existence of God, not as the fulfillment of their hopes and desires, but with dread bucking like a wild horse against the testimony of their reason:
You must picture me alone in that room in Magdalen, night after night, feeling, whenever my mind lifted even for a second from my work, the steady, unrelenting approach of Him whom I so earnestly desired not to meet. That which I greatly feared had at last come upon me. In the Trinity Term of 1929 I gave in, and admitted that God was God, and knelt and prayed: perhaps, that night, the most dejected and reluctant convert in all England.