I always loved C.S. Lewis’ idea of “mere Christianity”—that there are fundamental beliefs about God and Christ that bind the church together, even while so many of the particulars might be different or contradictory. It’s an idea that makes sense. And it’s comforting. It helps explains why Christianity as a belief system has managed to survive so many centuries and penetrate so many disparate cultures. There are certain core beliefs (amazing, world changing beliefs) that can’t help but endure. And as I’ve spent the last few days in Lewis’ house here in Oxford, his idea—“mere Christianity” is one I’ve thought about again and again.