When reading about Paul’s missionary travels in Acts, one is instantly confronted with a dizzying array of place names. Derbe, Lystra, Iconium, Phrygia, Galatia, Mysia, Troas, Macedonia, Samothracia, Neapolis, and Philippi—and that’s just the first 12 verses of Acts 16! Clearly, Paul took seriously “the work whereunto [the Lord had] called [him]” ( Acts 13:1–3 ) and felt an urgency to spread the...