You'll recall that katallagete is the Greek word for the imperative "be reconciled" from 2 Cor. 5.20. As the title of the periodical edited by Campbell and James Holloway, katallagete is the summation of Brother Will's message.
And what sort of message is that? Simply this: be reconciled, with everyone. More precisely, recognize that you are, in Christ, already reconciled to every human being. The goal, then, is simply to be what you are, a reconciled person.
If that still seems a bit vague, let me unpack it in three steps.
First, we recognize that reconciliation is a new social reality that has been created by Christ.
Second, we recognize that this reality eradicates all other human categories, group memberships, boundaries, or designations that may be interposed between two human beings--be those boundaries moral (saint vs. sinner), legal (criminal vs. law abiding), national (nation vs. nation), political (Democrat vs. Republican), religious (religious vs. irreligious), sexual orientation (straight vs. gay), racial (black vs. white), gender (male vs. female), economic (rich vs. poor), and on and on.
Because of the reconciling work of Christ these boundaries--these "worldly points of view" (2 Cor. 5.16)--no longer exist.
Third, we enact this new social reality. We live as if these social boundaries do not exist. We no longer regard anyone from a "worldly point of view." We live reconciled to everyone. Simple as that.
The practical upshot of katallagete, then, is something akin to the little way of St. Thérèse. Specifically, you don't have to do much of anything to be a Christian by way of mission or ministry. You simply have to live as a reconciled human being. And the simplicity here can be a bit shocking. Summarizing the ethic of katallagete Campbell and Holloway once described it this way:
Do? Nothing. Be? What you are--reconciled, to God and man. Katallagete.
Do nothing. Be reconciled. Simple at that. Thomas Connelly, in his biography of Campbell, shares the following observation from Brother Will in a passage where Brother Will is describing the incomprehension he would face giving lectures about katallagete on college campuses:
"Somebody is always winding up [the lectures I give] by saying to me, 'Reverend Campbell...what are the practical implications of your message? What are you saying to us? It sounds as if you are preaching that we should do nothing.'" Campbell smiled. "When I hear that, that is when I know I am getting through to them. That's when I say 'Brothers, now you are finally getting the message. Do nothing. Just be something. That is the whole message of being a real Christian anyway. Just be what you say you are--a Christian."