There have been challenges to the assertion of common authorship, largely on the grounds of vocabulary and style. Most notable is Albert C. Clark (The Acts of the Apostles: A Critical Edition with Introduction and Notes on Selected Passages [Oxford: Clarendon Press, 1933], p. 394), who, after a detailed study of the syntax and style of Luke and Acts, concluded “that the differences between Lk. and Acts were of such a kind that they could not be the work of the same author.” Wilfred L. Knox countered Clark’s arguments in a carefully constructed rebuttal, however. Like Clark, Knox deals with the use of particles, prepositions, conjunctions and other small parts of speech. Knox reasoned: “It may seem that to discuss such matters is to waste time over minute trivialities; but a man can be hanged for a fingerprint” (The Acts of the Apostles [Cambridge, UK: Cambridge Univ. Press, 1948], p. 3; also pp. 4–15, 100–109).

Other interesting linguistic dissimilarities between Luke and Acts have been more recently observed by Stephen H. Levinsohn, H. Levinsohn, Textual Connections in Acts,SBLMS 31 (Atlanta, GA: Scholars Press, 1987),who incidentally is not primarily interested in the authorship question.

Modern scholars generally affirm the position of common authorship held by the early church, though the implications of that common authorship are not always clearly distinguished. See, for example, Mikeal C. Parsons and Richard I. Pervo (Rethinking the Unity of Luke and Acts [Minneapolis, MN: Fortress, 1993]), who suggest that we must distinguish among various kinds of unity (e.g., narrative, generic, theological) when speaking of the unity of the Lukan writings and also allow for the possibility that some elements of discontinuity between the two writings might arise from time to time.