How much freedom does an individual have to change something of which they choose to be a part?
If, for instance, I am a Marine, how much freedom do I have to change Marine Corp’s beliefs and practices? If I said to the Corp “you’re way too violent, you need to plant roses instead of training with guns”, would they listen to me? Probably not. I am completely free to hold that belief with all my heart, but if I insist upon it so that I don’t train with soldiers but go off in my little garden and spend my days planting roses, I cannot with integrity consider myself a Marine.
We might also ask, should the Marine Corp listen to me? Should they stop training with guns and start planting roses instead? Some might think so. But if they did, they would no longer be the Marine Corp. They would cease to serve the purpose for which the Corp was created, having become a horticultural society instead of an elite military unit.
Or take another example. Say I belong to a catch and release (letting the fish go instead of eating it) fly fishing club. Do I have the freedom to be a member of that club even I choose only to fish only with worms and kill everything I catch?
It would not seem so. If I insist on using worms and killing everything I catch, there is no meaningful sense in which I could consider myself a fly fisherman who practices catch and release.
Should the club change to meet my personal beliefs and practices? Again, it would hardly seem so. If it did, it would cease to be what it was created to be, a community in which people rejoice in their shared love of fishing with flies and letting the beautiful fish they catch go to live another day.
A final example. How much freedom does an individual have to change the Gospel of Jesus Christ? I’d suggest the answer is directly analogous to the above examples. We do not change it; we submit to it. If we don’t submit to it, we may be many things, some of which are fine and good, but we are not Christians.
That’s what Peter is saying in today’s Gospel. Jesus is Lord and Messiah, raised from the dead by the supernatural power of God. For those who would faithfully follow him, only one response is possible: “Yeah and amen.” To say that any other answer is possible is to preach a false gospel, one that is not worthy of the name.