In the gospel for August 21 Peter is a rock; the Sunday after that Peter is a stumbling block.

This Sunday Peter is the heroic first believer, the leader among the disciples, who steps forward to answer Jesus’ question, “Who do you say that I am?” Peter answers, “You are the Messiah, the son of the living God.”

Next Sunday Peter is the lead antagonist, who rebukes Jesus for suggesting he will face conflict and death in Jerusalem but come through it “on the third day.”

This Sunday Peter is Bar Jonah, son of the prophet, a voice revealing who Jesus is; next Sunday Peter is Satan, open to the glory but not the cost of discipleship.

Only the gospel of Matthew gives us the image of Peter as a rock. In all three synoptic gospels Jesus asks his disciples, “Who do you say that I am?” In all three synoptic gospels Peter answers, “You are the messiah.” Only in Matthew does Jesus add, “You are Peter and upon this rock I will build my church.” It’s an irony that Peter, the apostle whose failings we know best, gets the image of being a rock.

Peter is all hurrahs that Jesus is messiah but conflict and suffering—no. He doesn’t see the cost of bringing good news to the poor and preaching reform.

Peter, the impetuous, bounds out of the boat at Jesus’ invitation and walks on water until he looks and sinks like a rock.

Peter is certain he will stand by Jesus no matter what, then denies knowing Jesus rather than put his life at risk during Jesus’ trial.

Rock is a pun on Peter’s name but the image is contrary to his character and leadership. Peter is a learner, not a granite head. Peter’s tongue catches fire with a new message on Pentecost. He is fiery and responsive to the Spirit. Peter disregards Jewish law and visits the home of the Roman Centurion Cornelius. As he tells Jesus’ story, Peter sees the Holy Spirit poured out upon Cornelius and his whole household, so he baptizes and welcomes these outsiders into the Christian community. He is innovative and responsive to the Spirit.

Peter, the learner, approves Paul’s insistence that Gentile Christians need not keep the Jewish law. Far from being an impenetrable blockhead and rock, the Peter of history responds to the transforming power of Jesus and the Spirit in his life.

It is Matthew as he writes 25 years after Peter’s death that attaches this rock saying to the story of Peter’s response to Jesus’ question, “Who do you say that I am?”, making a rock of certainty of this innovative leader who spread the gospel into new frontiers. It is we who must notice that two chapters later in Matthew Jesus gives the authority to lose and bind also to the Christian community.

Today the Spirit pushes us like Peter to new frontiers. Vatican II called forth the people of God to full and active participation in the Church’s worship and life in the world. The rise of the laity—us—but we shouldn’t use that word laity because it means second class and we aren’t. We are baptized and called to holiness. How much participation of the people is too much? Leadership today arises from the grassroots as surely as from the top down. It is our obligation to lead in all the ways we can—to speak out, to act with compassion, to organize for the common good. We live under democratic governance in our country but under monarchial governance in the Church. Where is the Spirit that led Peter to Cornelius beyond the limits of Jewish law leading us? The frontiers hold tensions and conflicts.

Some people inevitably return to past answers and drop anchor in an earlier century. John Allen, the Vatican correspondent, estimates the Church will remain very conservative for 50 years. The Spirit will not let others rest.

We no long live in religious silos. Our neighbors may be Hindu, our coworkers Buddhist practitioners, and our clerk at the store a Muslim. What is the Christian mission in this new context? Who is Jesus in relation to Krishna or Buddha or Confucius?

The new evolutionary cosmology does a job on rocks of unchanging certainty. Now our cosmic history reveals God is creative and dynamic. Evolution happens though both pattern and chance, through law and freedom. We see the holy in all that is. No more do we divide matter and spirit. We have new questions like when does incarnation begin? Nine months before Jesus’ birth or at the big bang when the energy that animates all that is bursts forth and begins to unfold? The work of considering the Christian story within the frame of the evolving universe story is ongoing.

How do we develop skills for cherishing our differences and holding conflicts in tension rather than resolving or eliminating them as we do in competition. What if we trained for dialogue and negotiation the way Olympians do for sports?

Theologian Karl Rahner fifty years ago said that in the future Christians will be mystics or they will not be Christians at all. We have in Peter a model mystic who experienced the living God in Jesus, in the Spirit, in Cornelius, in Paul. Mystics are not weird visionaries but people who must seek the deepest truth for themselves. Mystics live consciously and pay attention to what troubles or torments them and what energizes them and gives them life. A mystic experiences the mystery that opens the future and that religious people call the living God.

I want to suggest a contemporary, organic image that expresses our call as Christians. Recently I visited urban kids working on a farm growing plants from heritage seeds their Native American elders have saved. I am visiting in the kitchen when the director pulls her worm colony out from under a table—a big box. She’s growing worms to help turn her compost heap into new, fertile topsoil.

The same week the newspaper features a friend’s permaculture garden. She, too, has a worm colony. I feel behind, wondering if everyone but me has worm colonies and isn’t telling me. Compost includes grass clippings, unused or rotten parts of vegetables, weeds, leaves, stuff that gets too old. We live immersed in compost, in all the writings, songs, images of the past. We are always making more out of what is. Is it too humble an image of us at the grassroots of our evolving Church to think of ourselves as a worm colony—called to transform all the garbage, the compost, into fertile ground?