When trying to make sense of the changes that new media have brought to us, we can use either supplementary or substitutionary logic. With supplementary logic, Facebook et al. extend the range of our embodied relationships; with substitutionary logic, social media  replace them. Those who want to use social media to enhance their churches' outreach implicitly use supplementary logic. Those who want to worship online and don't want to change out of their pajamas or meet other people in their messy particularity ... well, you get the idea.
A recent trip to New York City for a first meeting of the New Media Project Research Fellows reminded me of the superiority of supplementary to substitutionary logic. This happened because the neighborhood around Union Theological Seminary is so deliciously, specifically, embodiedly particular. Union itself is a marvel: its gothic architecture makes it unmistakable that this is a place with history. Niebuhr taught here; Bonhoeffer smoked and worried and decided to go home here; James Cone and Christopher Morse teach here; Serene Jones leads here. The neighborhood extends this particularity; the Jewish Theological Seminary, down Seminary Row, has a glorious crest above its door: "And the bush was not consumed." A tunnel under Union leads you to the grandeur of Riverside Church , where Fosdick and Forbes thundered. Go a few blocks south and east, and you're at The Cathedral of St. John the Divine, the largest interior church space in North America. The morning I visited, the light shone blue through the rose window, filling the clerestory with incandescent beauty. The chapel at Columbia University, with its stained glass above the altar depicting St. Paul preaching on Mars Hill, is a perfect image for situated Christian truth vis-à-vis the gods on campuses and in Manhattan.
One afternoon a friend and I took a trek north and east to Abyssinian Baptist Church where Bonhoeffer learned  from African Americans how to hope and not despair in the face of oppression. He learned from the best of teachers; this great church was formed by African Americans and Ethiopian merchants in the early 1800s who would not be segregated. Adam Clayton Powell and Samuel Proctor preceded Calvin Butts in the pulpit. An attendant at first demurred at our request to peek in: tourists couldn't visit the day we were there. After a little begging and pleading, she let us in and showed off her house of worship.
Why am I going on at length about all this?
I've heard of all these places. I'd visited one or two. But there is something about visiting them again, seeing them with my physical eyes, walking around them with my own two feet (Bonhoeffer walked this far from Union to Abyssinian on Sundays?), that is irreplaceable. One could take a virtual tour of each of them at any time from any spot on the globe. But a physical, fleshy way of being with these buildings and histories matches a physically-saving savior who takes our flesh and bone to make them holy.
The Web is a marvel -- a good gift to be put to use. But like all good gifts, it is dangerous. One way we can counter that danger is to walk around where we live and in places we visit. And one way to measure its goodness is to ask how it enhances our bodily, face-to-face relationships with God and neighbor.
And to make sure we never, ever, speak of it as a substitute for church.
Jason Byassee , a research fellow for the New Media Project, is a research fellow in theology and leadership at Leadership Education at Duke Divinity School . The New Media Project at Union Theological Seminary  is a research project helping religious leaders become theologically savvy about technology.