The Roman emperor, according to Paul, “exalts himself above all that is called God or that is worshiped” (2 Thess. 2:4a). Just a few years before Paul writes, the public receives warning of the evil potential of emperor worship, when the emperor Caligula (a.k.a. Gaius) attempts to place his image in the Temple in Jerusalem (Josephus, Ant. 18:8:2-3).
The phrase “so that he sits as God in the temple of God, showing himself that he is God” is interesting. When hoste (“so that”) is followed by an infinitive (kathisai, “to sit”), it indicates a purpose intended — not necessarily a purpose accomplished.  As Moule puts it: “Strictly speaking the Infinitive should indicate only the potential result, representing the inherent qualities of the situation and not necessarily the actual consequences.” 
Earlier it was Caligula’s intention to sit in “the temple of God” in Jerusalem to “show himself that he is God.” In fact, Philo tells us that “so great was the caprice of Caius [Caligula] in his conduct toward all, and especially toward the nation of the Jews. The latter he so bitterly hated that he appropriated to himself their places of worship in the other cities, and beginning with Alexandria he filled them with images and statues of himself.” 
In my next blog I will show how this applies to Nero Caesar.
 As in Luke 4:29, where the Jews led Jesus to a hill “so as to cast him down” (hoste katakremnisai auton). W. E Best, Commentary on First and Second Thessalonians, 286-290. H. E. Dana and Julius R. Mantey, A Manual Grammar of the Greek New Testament (Toronto: Macmillan, 1955), 214. Robert W. Funk, ed., F. Blass and A. DeBrunner, A Greek Grammar of the New Testament and Other Early Christian Literature (Chicago: University of Chicago Press, 1961), § 391 (3).
 C. F. D. Moule, An Idiom-Book of New Testament Greek (2d ed.: Cambridge: Cambridge University Press, 1960), 141.
 Philo, Legatio ad Caium 43, as cited by Eusebius, Ecclesiastical History 2:6:2.