Tae Hun Kim, «The Anarthrous ui(o\j qeou= in Mark 15,39 and the Roman Imperial Cult», Vol. 79 (1998) 221-241
This article points up evidence by which the language of the Roman imperial cult might help make clearer what a reader of Mark's Gospel might understand when the centurion (Mark 15,39) refers to Jesus as ui(o\j qeou=. Knowing how an audience familiar with this cult language would react, Mark intentionally speaks of Jesus as ui(o\j qeou= at 1,1, as well as at 15,39.
However, this is not to say that the centurion was not fluent in Greek and thus omitted the definite article due to Latinizing influence, because there is a reasonable possibility that the confession was made originally in Greek. Although by law only Roman citizens could serve in the legions, shortage of manpower in Italy made it necessary for the legions to recruit locally. There were ever increasing numbers of non-Roman citizens enrolling in the legions with the promise of Roman citizenship at the end of their service. Among others, the eastern legions stationed in Asia Minor and Syria were almost entirely composed of Greek-speaking locals 12, and these were the legions responsible for the defense and administration of Judea at the time of Jesus. So there appears to be a fair chance that the Roman centurion in Mark 15,39 was not a Latin-speaking Roman national but a Greek-speaking native and thus made the confession in Greek. It seems plausible, therefore, that the absence of the definite article in Mark 15,39 was deliberate and not accidental on the part of either the centurion himself or the Markan author.
Divi filius (or qeou= ui(o\j) in the context of the Roman imperial cult
The relationship between some of the literary features in Mark and the languages of the Roman imperial cult has been investigated by a number of scholars, and some have argued that the anarthrous ui(o\j qeou= in Mark 15,39 refers to the emperor. P. Bligh has argued that at the scene of the crucifixion the centurion gave the final verdict concerning Jesus in the words of the imperial title: This man, not Caesar, is the Son of God!13. In my opinion, however, the evidence seems to suggest that the title son of god (ui(o\j qeou=)' was unique to Augustus, a title with which no other emperor, with the possible exception of Tiberius, could be associated, and thus it cannot be loosely applied to the Roman emperors in general as the object of state cult. Any Roman emperor could claim to be a god of some sort and was hailed by his subject as one, especially in the Eastern provinces; but the name son of god was reserved only for Augustus because it was a personal name, not a mere title, that he assumed when he succeeded his deified father Julius Caesar.