What does Acts 17:28 mean?

Paul is in the Areopagus. There, he explains to Stoic and Epicurean philosophers that the Creator God of the universe is near enough to us to want a relationship, but magnificent enough that His likeness cannot be confined to a handmade idol. He has explained that God not only gives life and breath to everything, but He also established the times and places for people and nations to exist for the purpose of inviting them to seek Him (Acts 17:22–27, 29).

His first quote is by either Epimenides of Crete or an unknown Athenian poet. It is from the verse:

They fashioned a tomb for thee, O holy and high one— The Cretans, always liars, evil beasts, idle bellies!— But thou art not dead; thou livest and abidest for ever, For in thee we live and move and have our being.

It shows that the Creator must be "near" because He is our source of life and animation. The fact that He gives us life means He is greater and yet like us.

Paul's second quote is from the opening call to Zeus in the poem Phaenomena from the Cilician Stoic Aratus:

Let us begin with Zeus. Never, O men, let us leave him unmentioned. All the ways are full of Zeus, and all the market-places of human beings. The sea is full of him; so are the harbors. In every way we have all to do with Zeus, for we are truly his offspring.

The Stoics in Paul's audience so believe that all mankind are Zeus's offspring, they insist slaves are equal to citizens and freedmen.

If God is the source of our movement and being, and if we are His offspring, it's illogical to make images of Him by human hands (Acts 17:29). Paul shows that idols don't make sense even within the Athenian belief system.

Instead, Paul calls the Athenians to repent. They have disrespected God and need to acknowledge their sin of idolatry. Just as God set times for individuals and nations, He set a time for future judgment. He affirmed this by selecting the judge and identifying Him by raising Him from the dead (Acts 17:30–31).

This is a step too far for most of the philosophers. Epicureans and Stoics didn't believe in judgment or the resurrection of the dead. They mock Paul while he walks away (Acts 17:32–33).