"Rick Rubin has a larger looming presence on this album than his 'thank you' deserves. He asked 'Why can't more people cover U2 songs?' And it's because, with all the great sounds and arrangements, you can forget that there isn't a song there."
- Bono on Rubin's influence on Songs of Innocence
The Popmart stage design, which looked like a supermarket, appealed to Bono as a supermarket, with its myriad choices and temptations, could function as a metaphor for U2's songs, as they often deal with the struggle between desire and faith.