One God, One Lord
When we are used to thinking in a certain way, we assume that is true and normal. The new Christians in Corinth had been brought up from childhood to believe that the many pagan gods were real and had real power, which is why they were worshipped and sacrifices made to them. So the gospel brought a massive personal and cultural change. Paul taught that there is only one God (Deuteronomy 4:39) and that the so called 'gods' of Greek and Roman culture, and the mystery 'gods' of the tribal religions, had no reality, personality or power (Psalm 135:16-18).