See esp. Joseph Fitzmyer, The Gospel According to Luke: Introduction, Translation, and Notes, Anchor Bible 28 (Garden City, NY: Doubleday, 1981), vol. 1, pp. 35–59; and Luke the Theologian: Aspects of His Teaching (Mahwah, NJ: Paulist, 1989), pp. 1–26. Fitzmyer offers a carefully and critically nuanced defense of the tradition: Luke the physician was an uncircumcised Semite and sometime companion of Paul.