Paul is urging the Philippians to take on a mindset of humility. Now, humility (lowliness) was no more a virtue in Paul’s Roman world than it is in our own world. Before understanding how to define the “humility” Paul means, we need to understand what it does not mean.
We’re not talking about some kind of an “underdog” kind of lowliness that Americans love – the kind you might find in someone not expected to succeed, who rises up and conquers all his or her foes. This is not about Superman, or Spiderman, or Batman, or some other superhero, hiding their identity, while relying on their own strength to get things done.
Nor are we talking about some "obsequious sycophant" (as one commentary put it) – in other words, someone who changes to be whatever you want them to be in a self-effacing way. An example would be the cowering toady in the Disney movie 101 Dalmatians. Cruella DeVil asks, “What kind of sycophant are you?” to which the toady replies, “What kind of sycophant would you like me to be?” This is false humility, arising from fear, with no heart to do what is right.
The humility Paul tells us to pursue is the opposite of that kind of selfish ambition that, for instance, might cause someone to preach the gospel for personal advancement. Paul mentions exactly this kind of selfish ambition in the previous chapter where he says,
Some indeed preach Christ from envy and rivalry, but others from good will. The latter do it out of love, knowing that I am put here for the defense of the gospel. The former proclaim Christ out of selfish ambition, not sincerely but thinking to afflict me in my imprisonment.
Paul asks us to set our ambitions aside, and replace them with love, unity, and the respect of honoring one another even above yourself. Of all the gifts and abilities God has given you, Paul teaches you to empty yourself of all the identity you can have in those gifts, and instead employ those gifts as a servant to others.