In a 1762 letter to a Methodist he called Miss Furly, John Wesley sought to counter some false teaching about the nature of perfection.
[S]anctification … does not include a power never to think an useless thought, nor ever speak an useless word. I myself believe that such a perfection is inconsistent with living in a corruptible body: For this makes it impossible “always to think right.” While we breathe, we shall, more or less, mistake.
In reading Wesley, it is remarkable how much time and energy he had to spend explaining this point. The word “perfection” was a constant thorn in the side of his theology because he had to constantly explain what it did not mean and clarify what it meant.
I want you to be all love. This is the perfection I believe and teach. And this perfection is consistent with a thousand nervous disorders, which that high-strained perfection is not. Indeed, my judgment is, that (in this case particularly) to overdo, is to undo; and that to set perfection too high, (so high as no man that we ever heard or read of attained,) is the most effectual (because unsuspected) way of driving it out of the world.
I like that phrase “to be all love” as a summary of his doctrine of perfection. But we must make sure to remember that it is love directed both to God and our neighbors. When we are all love, we love God. And we love God by keeping his commands.
With that caveat, though, I think “to be all love” is as good a description of perfection in Wesley’s theology as any I have read from his or other pens. It reminds us of the totality of love. It reminds us of the centrality of love. I prevents us from fixating on things that are not love. It reminds us that Christianity is a matter of the heart.