Jesus humbled himself by taking on the nature of a human. While humility is often seen as a virtue in modern culture, people did not “humble themselves” in the Greco-Roman world. Someone who was humble was lowly and weak, even servile. That man should humble or belittle himself is rejected. To suffer misfortune and humble oneself “is quite unnecessary, vain and irrational” (Plutatch De exilio, 1 (II, 599b). In the Hebrew Bible, to “be humbled” is associated with punishment. God humbles the proud (1 Sam 2:7). The word appears in LXX Isa 53:8, describing the humiliation of the suffering servant.
Not only did Jesus become a slave, he was a slave who was executed by crucifixion, the most shocking horror in the Roman world. Jesus therefore goes from the highest place imaginable, equality with God, to the lowest, death on the cross.
Because he was obedient and suffered innocently, God vindicated Jesus exalting him to the highest place imaginable. The verb Paul uses for “exalted” (ὑπερυψόω) is not the usual one in the New Testament, it only appears here, but it also in Ps 96.9 (the verb is repeated many times in Odes 8:52-88). It is possible Paul has this verse in mind in Phil 2:9-11, the Most High ὁ ὕψιστος of that verse is God himself, and he is exalted above the earth and far above all other gods. This exaltation refers to the resurrection (cf. 1 Cor 15), but also the ascension in Acts 1 and Rev 4-5.
Because he was obedient and suffered innocently, God gave to Jesus the highest name imaginable. In the Roman world the name of the emperor was venerated as divine on coins and inscriptions. Yet Jesus has been given a name that is above every name, including the Roman emperor! And because he was obedient and suffered innocently, God will put everything under the Lordship of Jesus. Heaven, earth, and under the earth all will acknowledge that Jesus is Lord.
All this implies that Caesar is not the true lord of this world. Paul was not anti-Rome, although his gospel did subvert the social order by advocating Jesus as the Lord. As I read Paul, I think Hellerman (Embracing Shared Ministry, 168) is right that Paul is not consciously anti-Imperial, he in no way was advocating some sort of rebellion against the Empire. But the Gospel was so radical that it would erode the Empire if that Gospel practiced consistently. Perhaps the sad story of Church history is that by the time Christianity was the majority religion, it had become thoroughly Roman with respect to honor and status.
Jesus is therefore the true Lord of this world and all of creation ought to recognize that lordship. It is quite remarkable that Paul never suggested the Christians openly rebel against Rome. That would have been a futile effort since there were so few Christians. What he did tell the Philippian church is that they ought to have the same attitude as Jesus. This sort of humility was counter to the Greco-Roman world and slowly brought down the Empire.
More important, this sort of humility is counter to Western/American culture, even in the church. If Paul says “Jesus is Lord, Caesar is not,” should we also say, “Jesus is Lord, America is not”?