Early Greek religion was a blend of the Achaean, Dorian, Minoan, Egyptian and the Asian cultures, and came about as a result of the mingling of these cultures. Their belief was that each city was under the protection of one particular god, who was worshiped with unique emphasis in that city. Athena is the goddess of Athens, Artemis is the god of Sparta, Aphrodite was worshiped at Corinth, Apollo worshiped at Delphi and Delos, and Zeus, the king of gods, was worshiped with special reverence at Olympia.
Paul traveled through Greece with Silas and after some trouble with the Jews for preaching the gospel, he was sent to Athens to wait for Silas and Timothy. (Acts 17 )
While Paul was waiting for them in Athens, he was greatly distressed to see that the city was full of idols. Acts 17:16
Paul wanted to present the gospel in a way that was relevant to the people so he chose the culture's dedication to religion.
"For as I walked around and looked carefully at your objects of worship, I even found an altar with this inscription: TO AN UNKNOWN GOD. Now what you worship as something unknown I am going to proclaim to you." Acts 17:23
Paul used that as his opening remark to tell the people about the salvation that comes from Christ. He didn't join in their customs and practices, but rather, he pulled something out from it. He wasn't trying to add another god to their extensive collection of gods. He was taking a step to change the culture and it's practices. He was introducing the Unknown God, Jesus Christ, to the people with the full intent of displacing all other gods, beliefs, and religious practices in the culture. Alistair Begg with Truth for Life stated it this way, "Becoming a Christian involves a radical transformation and a break from all non-Christian habits. Becoming a Christian does not mean simply adding a Jesus package to a lifestyle of our own choosing."
With the onset of Christianity, the Greek religion slowly became extinct. This happened because the believers turned away from the practices of the culture and taught new believers to do the same. Do we, as followers of Jesus Christ, do that in this culture? Do we try to displace any evil that sets itself up against Jesus, or do we accept it, tolerate it, and even embrace it while we set up our belief system right next to it?
"...and when the LORD your God has delivered them over to you and you have defeated them, then you must destroy them totally. ...for they will turn your sons away from following me...This is what you are to do to them: Break down their altars, smash their sacred stones, cut down their Asherah poles and burn their idols in the fire. For you are a people holy to the LORD your God. The LORD your God has chosen you out of all the peoples on the face of the earth to be his people, his treasured possession." Deuteronomy 7:2,4-6