When my son was younger and he’d go out to town for a drink with his friends sometimes he would come home let’s say a little the worse for wear and be sick or spend the next day recovering in bed with a hangover. When he did I would say to him “you know your trouble don’t you, you don’t have the brains you were born with." Now unless he had had a lobotomy that statement does not make much sense! Of course he had the brains he was born with. But what I meant was that he had the brains but didn't use them.
In other words he'd left his brains at the door of the nightclub and stopped thinking about the consequences of what happens when you have too much to drink. He had the intelligence to know what was sensible but he didn't use it.
Paul is saying something along the same lines to the Philippians. As Christians - those who are as Jesus said “born from above” (John 3:3) or who are what Paul likes to describe as "in Christ Jesus" - they already
therefore had his mind. What they needed to do now was to live it out.
So as Jesus is humble so they ought to be humble. As Jesus had the attitude of a servant so they should be willing to serve. As Jesus was obedient to God so they ought to obey God. If they are indeed “in Christ” —if they are Christians - then the presence of Christ IN THEM means that they already have his mind, they just needed to live out of it.
The Philippians seem to have forgotten that and so Paul is reminding them to live according to the life and character of Jesus which they already have within them by virtue of their Christian faith.
And we too as Christians now, are called to live out the life of Jesus which has been given to us and is ours in Christ. When we do then the world will sit up and take notice and see that being part of God's church really does change people for the good. And if it changes people, then it will change the world.
So let’s take to heart what Paul is saying: “Have this mind among yourselves, which is yours in Christ Jesus.” Become more like the Christ within. Amen