Most Christians, if forced to answer the question posed above, would probably be able to articulate—and rightly so—that a certain “Luke” is the author of Acts. At the same time, however, they’d probably be surprised to learn that the book nowhere mentions this name. In fact, along with the four canonical Gospels, Acts is widely regarded, especially in liberal circles, as an anonymous work.
Is Acts truly anonymous, though? If not, who wrote it? And what do we know about the author?
Two matters shed light on the problem at the outset. First, even though Acts lacks an explicit ascription of authorship, the book would not have been “anonymous” in the first century. It’s likely that early churches would have known its author on the basis of personal relationships and/or oral tradition, much as the second-century AD book History of Alexander was known as Arrian’s without any ascription confirming that notion. Arrian even defended his omission with the following words: “I need not write my name, for it is not at all unknown among men, nor my country nor my family” (1.12.5). Second, the anonymity of Acts is probably a deliberate literary feature on the author’s part, which distinguishes the book from its secular Greco-Roman counterparts. As New Testament scholar Eckhard Schnabel writes,
A comparison with Greek and Roman historiography shows that in contrast to the motivation of secular authors to earn praise and glory for their literary achievements, the authors of the Gospels, as well as the author of the book of Acts, probably adopted the literary device of anonymity because “they regarded themselves as comparatively insignificant mediators of a subject matter that deserved the full attention of the readers.”
The tradition that Luke, a long-time companion of Paul, is the author of both the third gospel and the corresponding book of Acts is well established—unanimously even—as early as the second century AD. It can be found, for example, in the Muratorian Canon (34–35), the Anti-Marcionite Prologue to the Gospel of Luke, Irenaeus’s Against Heresies (3.1.1; 3.14.1–4), and Clement of Alexandria’s Miscellanies (5.12). This is confirmed from the ninth century on, when scribes began to include “Luke the Evangelist” (Louka euangelistou) in the Greek title of the book.
Interestingly, the New Testament makes only three explicit references to a “Luke,” and we can reasonably assume that they all refer to the same person. Philemon 24, for instance, identifies this figure as one of Paul’s “fellow workers.” Second Timothy 4:11 depicts him as Paul’s only remaining companion near the end of his Roman imprisonment. And Colossians 4:14 describes him as “our dear friend Luke, the doctor.”
The name Luke is an English form of the Greek name Loukas, which itself is a shortened form of the Latin Lucius. Since Jews in first-century Greco-Roman society often had both Greek and Roman names, the use of this name does not tell us in and of itself whether Luke was a Jew or a Gentile. However, if Colossians 4 is any indication, Luke was probably a Gentile. There, in the final greetings of the letter, Paul cites Aristarchus, Mark, and Jesus Justus as his “only Jewish coworkers” (vv. 10–11). Only after that does he send greetings from Epaphras, Demas, and Luke (vv. 12–14). If this is right, then Luke may have been either a Gentile convert to Judaism or a so-called “God fearer”—a Gentile who had close ties with local synagogues.
A tradition as early as the late second century suggests that Luke was originally from Antioch, the capital of the Roman province of Syria. This remains plausible to this day. Not only did this city boast a large Jewish population in the first century, it also provided the means of attaining the level of education indicated by Luke’s linguistic and historical abilities (Luke 1:1–4).
The fact that Luke was a physician does not tell us much about his social background. This is because a physician’s status in Greco-Roman society largely depended on his or her patients. In Schnabel’s words, “Physicians treating senators or the imperial family obviously enjoyed a higher prestige that physicians who treated slaves and often were themselves slaves.” Still, New Testament scholars are almost universally agreed that Luke inherited a fairly high social status. In fact, if he can be compared to any known personage of that society, it is the later Galen of Pergamon (AD 129–210). The son of a prosperous architect, Galen received an extensive classical education and later travelled around the Mediterranean region, collecting medicinal herbs and writing lengthy studies on medicine, philosophy, and linguistics. Like Galen, Luke engaged in historical research, wrote books in educated standard Koine Greek, and travelled throughout the Mediterranean world (see especially the so-called “we” passages in Acts: i.e., 16:10–17; 20:5–15; 21:1–18; 27:1—28:16). As classicist Charles Fornara writes, these activities “excluded all but members of the highest levels of society. Wealth and social contacts were essential to the craft.” Such wealth and status were probably exceptional within the early church. Indeed, Paul implies as much in 1 Corinthians 1:26: “Brothers and sisters, think of what you were when you were called. Not many of you were wise by human standards; not many were influential; not many were of noble birth.”
To summarize, then: We can reasonably affirm that the book of Acts was never truly anonymous; that it was written by Luke the Physician; and that the author was a Syrian Gentile with Jewish-Christian commitments. Of considerable means and social status, he was also a long-time companion of the Apostle Paul’s and a witness to many of the events recorded in the book.
 In what follows, I rely heavily on Eckhard J. Schnabel’s recent commentary on Acts (so titled) in the Zondervan Exegetical Commentary on the New Testament (Grand Rapids: Zondervan, 2012), 21–25. Quoted material is properly marked as such.
 Ibid., 22; citing Armin D. Baum, “The Anonymity of the New Testament History Books: A Stylistic Device in the Context of Greco-Roman and Ancient Near Eastern Literature,” Novum Testamentum 50 (2008): 23.