In his discussion of the imperial cult in Tom Wright notes that Domitian liked to be addressed as dominus et deus (“lord and god”)—a phrase “familiar to readers of John’s gospel” (341).
Domitian was emperor from AD 81-96. He revived the imperial cult, which had languished under Vespasian. Among other self-aggrandizing projects, he constructed an imperial temple at Ephesus, where, according to Wright, “fragments of what must have been a positively enormous statue of Domitian have come to light”. He also came down hard on foreign religions. Suetonius records that the tax on the Jews was “levied with the utmost rigour” (Suet. Dom. 12.2), and according to Eusebius, Domitian “became a successor of Nero in his hatred and enmity toward God”: he was “the second that stirred up a persecution against us” (Eus. Hist. eccl. 3.17). Tertullian accused Domitian of a rather half-hearted approach to persecution:
Domitian, too, a man of Nero’s type in cruelty, tried his hand at persecution; but as he had something of the human in him, he soon put an end to what he had begun, even restoring again those whom he had banished. (Tert. Apol. 5.4)
Suetonius maintains that Domitian was himself deviously responsible for the “lord and god” innovation:
With no less arrogance he began as follows in issuing a circular letter in the name of his procurators, “Our Master and our God bids that this be done.” And so the custom arose of henceforth addressing him in no other way even in writing or in conversation. (Suet. Dom. 13.2)
That Domitian actively encouraged the practice is sometimes disputed, but it is at least clear that it was customary for supplicants and sycophants to address him in this fashion:
For [Domitian] even insisted upon being regarded as a god and took vast pride in being called “master” and “god.” These titles were used not merely in speech but also in written documents. (Dio Cassius Hist. 67.4.7)
When he was on the point of being condemned, he begged that he might speak to the emperor in private, and thereupon did obeisance before him and after repeatedly calling him “master” and “god” (terms that were already being applied to him by others), he said…. (Dio Cassius Hist. 67.13.4)
Since the majority view is that John’s Gospel was written in Ephesus (see Irenaus Adv. Haer. 3.1.2) towards the end of Domitian’s reign, it is certainly worth considering whether Thomas’ exceptional confession “My Lord and my God” (ho kurios mou kai ho theos mou: Jn. 20:28) was not intended as a direct rebuttal to the popular, blasphemous and self-serving acclamation of Domitian as “my lord and my god”. In that respect it would be similar to the centurion’s ambiguous pronouncement following the death of Jesus: “Truly this was the son of God / a son of a god” (theou huios: Matt. 27:54).
The point of this observation is not that the Christological conclusion that Jesus is divine is thereby brought into question. It is rather that our Christology—our understanding of the “divinity” of Jesus—should take the polemical construction of the belief into account. There is a historical dynamic to the confession—and therefore a degree of contingency—that I think a narrative-historical theology might usefully preserve. Christology is confession before it is metaphysics, and confession is a political act.