Paul “contextualized” the gospel for his hearers, showing how it related to their own culture without compromising its content.
Today we often err on either one side or the other–failing to be culturally relevant, or failing to represent accurately the biblical message. Paul speaks to two groups of philosophers present, Stoics and (probably a smaller group) Epicureans; his faith held little common ground with Epicureans, but the Stoics could agree with a number of Christian beliefs.
Paul opens by finding some common ground with his pagan audience. It was customary to begin a speech by complimenting the hearers in the opening of a speech, the exordium. One was not permitted to flatter the Areopagus (the leading philosophical and educational leaders of Athens), but Paul would remain free to start on a respectful note. “Religious” meant that they were observant, not that he agreed with their religion (“superstitious,” in the King James Version, does not convey the right idea).
Then Paul turns to more common ground. During a plague long before Paul’s lifetime, no altars had successfully propitiated the gods; finally Athens had offered sacrifices to an unknown god, immediately staying the plague. These altars were still standing, and Paul uses this as the basis for his speech.
Paul borrows a technique from Jewish teachers who had been trying to explain the true God to Gentiles for several centuries before Paul. Non-Palestinian Jews sometimes reminded Gentiles that even they had one supreme God, and tried to show pagans that their highest religious aspirations were best met in Judaism. Stoics believed that God permeated all things and therefore was not localized in temples (cf. also Is 66:1). Stoics and Greek-speaking Judaism emphasized that God “needs nothing,” using the same word Paul uses in 17:25. Jews and many Greeks alike agreed that God was creator and divider of the earth’s boundaries and of seasons’ boundaries (17:26). (Stoics also believed that the universe periodically dissolved back into God, but on this there was no point of contact between them and the Bible or Judaism.)
Jewish people usually spoke of God as a father specifically to his people. But Greeks, Jews scattered among Greeks, and some second-century Christian writers spoke of God as the world’s “father” in the sense of creator; though Paul elsewhere uses the term more specifically, he adopts the more general sense of father as creator in this case (17:28-29). The quote from Epimenides in 17:28 appears in Jewish anthologies of proof-texts useful for showing pagans the truth about God, and Paul may have learned it there. (Greeks cited Homer and other poets as proof-texts in a manner similar to how Jewish people cited Scripture.)
But while Paul was eager to find points of contact with the best in pagan thinking for the sake of communicating the gospel, he also was clear where the gospel disagreed with paganism. Some issues might be semantic, but Paul would not ignore any real differences. Although philosophers spoke of conversion to philosophy through a change of thinking, they were unfamiliar with his Jewish and Christian doctrine of repentance towards God (17:30). Further, the Greek view of time was that it would simply continue, not that there was a future climax of history in the day of judgment, in contrast to the biblical perspective (17:31). Finally, Greeks could not conceive of a future bodily resurrection; most of them simply believed the soul survived after death. Thus Paul’s preaching of the resurrection offended them most (17:31-32). But in the end, Paul was more interested in winning at least a few of these influential people to genuine faith in Christ (17:34) than in simply persuading all of them that he was harmless and shared their own views.