‘The Cult of the Most High God’ (ϋψιστος). Many believe that ϋψιστος is simply a name given to many pagan-deities. Trebilco argues that in Acts16:16-18, the girl was talking about a pagan-god, not the true God. However, ϋψιστος implies monotheism and its Jewish use is overwhelming, Jews addressed God as Theos Hypsistos (LXX). Acts 16, θεου του ύψιστου, when cross-referenced with the sayings of the demons in Marks Gospel, is the Jewish God, not Pagan. Its likely ϋψιστος is a mergence of Jewish and Pagan beliefs where some Gentiles would be a part of, a group of people within the pagan/proselyte spectrum: God-fearers.
Jewish Historian, Josephus also mentions persons attached to synagogues:
‘[Jews] were constantly attracting to their religious ceremonies multitudes of Greeks, and these they had in some measure incorporated with themselves.’
‘But no one need wonder that there was so much wealth in our temple, for all the Jews throughout the habitable world, and fearers of God…had been contributing...’
I therefore believe that we can legitimately speak of ‘God-fearers’ as a category of people in the first century AD.
L.H. Feldman Josephus, Judaism and Christianity (Yamamoto, Tokyo, 1987)
L.H. Feldman Josephus, the Bible and History (Yamamoto, Tokyo, 1988)
L.H. Feldman The Omnipresence of the God-Fearers (Biblical Archeological Review 12, no.5, 1986)
E. M. Smallwood The Jews Under Roman Rule (Leiden, E. J. Brill, 1981)
Robert S. MacLennan and A. Thomas Kraabel, The God-Fearers – A Literary and Theological Invention,(BAR 12, no.5, September – October 1986)
I. Levinskaya, The Book of Acts in its First Century Setting. Vol 5, Diaspora Setting (Eerdmans, Grand Rapids, 1996)