What does Acts 17:18 mean?

Like the slaveowners in Philippi (Acts 16:21), the philosophers in Athens notice that Paul is promoting worship of a deity that is not authorized by the Roman Empire. In De Legibus, ii. 8, Cicero says, "…let no one have private gods—neither new gods nor strange gods, unless publicly acknowledged, are to be worshipped privately…" Unlike the slaveowners, they don't have any reason to use this against Paul: they find it interesting.

The philosophers use the plural "divinities" because they think Paul is teaching a God of healing named "Jesus" and another god named "Resurrection." If they'd realized their error from the beginning, they wouldn't have paid Paul any mind. Epicureans believed in materialism and annihilationism: that there is no true supernatural and when a person dies there is no soul or spirit to resurrect. Stoics believed everything is material, including the soul, which is made of fire, and at death the soul returns to logos, the foundational law of the cosmos. Neither believed in a final judgment of wrong behavior.

Epicureans are wrongly accused of teaching hedonism. They did not teach that since humans cease to exist at death they should indulge in any pleasurable behavior while living. Rather, they sought to reach a state of ultimate peace and enjoy life without worrying too much. Gods are far away and unconcerned with us, they said, so don't worry about them—they don't even remember humans exist, and there is no judgment after death. A fulfilled life, in the mind of Epicureans, includes just enough food, just enough comforts, peaceful friendships, and balance in all things.

Stoics were also materialists but believed in the logos—the natural law of the cosmos. They thought that if one could align their expectations with the logos, one could find fulfillment and avoid the disappointment that comes with striving against reality. Where Epicureans debated, Stoics meditated.

"Babbler" is from the Greek root word spermologos. Literally, it refers to a bird that picks up random seeds from the ground. Metaphorically, it refers to someone who wanders about the marketplace, picking up bits and pieces of different philosophies and mashing them together in an incohesive mess. Paul knows Greek philosophy, and it's possible that the philosophers know something of Judaism. This talk of resurrection and healing and sin, however, is too new; the classical philosophers don't see a cohesive framework yet.