The main motif of this poem is the speaker's relationship to the church as a physical place. This emphasis on the material structure of the church demonstrates that the speaker doesn't have the religious knowledge necessary to know how the place is supposed to affect him spiritually. In line 11, he looks up at the church's roof and is surprised to find that it looks pretty new. He then wonders if the thing has been completely restored, or just cleaned. He quickly gives up on this question, though, musing that "Someone would know: I don't" (12). This kind of verbal shrug is a symbolic statement because he's not just talking about the roof here, but about his ignorance of the Christian religion. In other words, he might wonder what the significance of the church truly is, just before he admits that he doesn't know. In this sense, the empty church also suggests that somewhere in the world, there might be a true believer who could convince the speaker about religion. But this person is always absent from the building, just as faith is absent from the speaker's mind.
Line 2: The speaker steps into the church and lets the door shut behind him, showing a certain carelessness in his treatment of the building.
Lines 11-12: Just as he's interested in the church "stuff" as a bunch of quirky objects, the speaker seems more interested in practical things like the condition of the church's roof than in the spiritual significance of what he sees.
Line 24: Here, the speaker discusses what'll become of churches after all the believers are gone, and he thinks that society will keep a few of the major buildings on show for the purposes of heritage or history.
Line 37: After asking what will become of churches when no one believes in religion anymore, the speaker talks about how grass and weeds will take over the churches, and the unique shape of the churches will start to crumble and become less recognizable as time goes on. On a symbolic level, this also represents the way that religious faith will crumble over time and slowly become less recognizable as it decays.
Lines 51-52: The speaker wonders what the main purpose of the church is: to give meaning to birth, marriage, or death? But when he refers to the church as a shell, he might suggest that the church symbolically protects people from the harsh world. He might also suggest, though, that the church is ultimately an empty shell, with no deeper meaning.
Line 55: The deeper meaning of the church will never be totally gone, says the speaker, because people will always look for something that makes life seem like something more than a big joke. People need to take their lives seriously, and religion provides the framework for them to do so.
Lines 61-63: In these final lines, the speaker admits that even if he doesn't believe in religion, he still has to respect the fact that for thousands of years, millions of people have come to churches for a sense of spiritual meaning.