 or agendas. Of course, even the serious historians such as Polybius and Thucydides did not record verbatim transcripts of all of their speeches. It is unlikely that such accuracy would be possible. They could not avoid using their own style and summarizing. Yet, as stated by C.W. Fornara, "[t]he principle was established that speeches were to be recorded accurately, though in the words of the historian, and always with the reservation that the historian could 'clarify." The Nature of History in Ancient Greece and Rome, page 145.
So, there were ancient historians who took seriously the task of portraying speeches as accurately as possible. The question becomes, then, whether Luke was one of such historian. The evidence demonstrates that he was.
An Examination of Luke's Use of Speeches
A. Luke Relied Heavily and Faithfully on Speech Material in the Gospel of Luke
Although we have few of the sources Luke relied on to draft Acts, thus impairing a source-critical evaluation of that book, the same is not true for the Gospel of Luke. Almost no respected scholar questions the unity of authorship between Luke and Acts. And it is clear that Luke faithfully used pre-existing sources for when writing the Gospel of Luke. Moreover, the Gospel of Luke is--like Acts--largely driven by discourse. Luke clearly uses Mark and Q faithfully, though conforming their style to his own. As Paul Barnett has written:
It is widely believed that the Gospel of Mark predated and was used by Luke in his Gospel. This means that we have an objective means by which we can measure Luke's use of texts that were at his disposal. Of course Luke has his own purpose in writing, which he does not disguise. Yet when passages in Luke are set alongside passages from Mark, Luke proves to have been a sober and careful scribe.
Jesus and the Rise of Early Christianity, page 209.
The same is true of Luke's use the Q source, which scholars have easily detected by comparing the Gospel of Luke with the Gospel of Matthew, and even his own special materials. Many scholars have concluded that Luke's special source--L--was faithfully utilized in the Gospel of Luke. See Kim Paffenroth, The Story of Jesus According to L; Robert E. Van Voorst, Jesus Outside the Gospels, page 136-143. Indeed, "[a]lthough there are minor changes, there is no evidence that Luke has invented material not found in his sources. Indeed, the gospel as a whole shows no evidence of such a tendency, and in view of this it is a fair assumption that he would not have resorted to it in the continuation in Acts." Donald Guthrie, New Testament Introduction, page 380.
In sum, when evaluating the speeches in Acts, "we have to reckon with the demonstrable factor that Luke used sources for the spoken word, and used them rather conservatively." Colin Hemer, Acts in the Setting of Hellenistic History, page 426. That Luke relies on preexisting source material for his speech material in Luke strongly suggests that he was among those ancient historians who believed it was his responsibility to portray speeches as accurately as possible.
B.     Luke Uses a Style Similar Accuracy-Minded Ancient Historians
As an educated Greek, Luke was likely aware of the writings of Polybius and Thucydides, and their efforts to accurately transmit speeches. Moreover, a comparison of Luke's style with other ancient writers demonstrates that "Luke's Greek style is in various ways like that of the serious Hellenistic historians, Polybius in particular." Ben Witherington, The Acts of the Apostles, page 43. Moreover, "[t]his is important because style was an important indicator of how a work should be evaluated in antiquity. Luke's style suggests that he wishes to be heard as a serious Hellenistic historian would be heard, like a Polybius." Ibid.
Of all the historians writing in Greek, Luke's work seem to  be most like the Greek historiography of someone like Polybius, and, to a lesser degree, Thucydides. Indeed, a reasonable case can be made that in terms of method, style, and type of historiography Luke is following this particular Greek tra