The chapter was Acts 16 and, I tell you, the English Standard Version, Study Bible is terrific when one is short on research time. My one problem with this thick book is that it doesn't open wide enough to see easily the notes they've crammed in the inside margin. I have to press the page down really flat to see it. I'd rather reference a book I don't need to keep a hand on.
The first question instructed one to trace the path of Paul's second missionary journey, begun in the previous chapter, on a map. I've never taken any interest in the details of Paul's trips so this was as good a time as any to learn them, to follow along on paper. The point was how "unusual" his path was, consciously guided by the Holy Spirit (Acts 16:6). I think this is because Paul wanted to avoid areas evangelized by Peter (2 Cor. 10:16; 1 Peter 1:1). The decisions at Jerusalem in the previous chapter were for "believers in Antioch and throughout Syria and Cilicia (15:23) but since the issue of Gentile converts affected all the churches, Paul reported those decisions" in other cities. [ESV footnote]
The point of Keller's material is the diverse types of people Paul reached and the methods by which he reached them. Lydia, a God-fearer or convert, who worshipped the one true God was reached through Scripture study and discussion. The Pythoness (Gk.: πνεῦμα Πύθωνος) was (possibly) possessed1 and not free, as her owners exploited her oracles for personal gain. Paul exorcised her, much to the dismay of her handlers. The Philippian jailer seemed to fit in between these two, neither religious nor evil. He was reached by Paul's character. Always, their immediate needs were met first but presumably Paul gave the "full picture" by and by (cf. 16:32).
The "thought" question came towards the end:
"Why does Paul insist on a public apology v. 37?"My own answer took a dramatic approach to the text: the apology foreshadows Paul's "going to Rome" as a citizen of the Empire which is his undoing. However, I had read Keller's answers in preparation before class after making out my own answers so as to avoid anything "too wrong." I offered his answer as a correction to my own and so let my small group leader know I had access to the "official" answers (that's just how I am). So then, the civil apology is important for the freedom of the church Paul left behind. Without it, the church was founded by a criminal. And it turns out that the church at Philippi seems to do the best of all the communities, even into the sub-apostolic period.
1 I was surprised at the "explaining away" of demon possession that occurred in our small group.