Permutation City by Greg Egan
Francesca said, "Don’t you ever want to give thanks to God, when things are going well for you? Don’t you ever want to ask God for strength, when you need it?" "No." "Well, I do. Even though I know God makes no difference. And if God is the reason for everything, then God includes the urge to use the word God. So whenever I gain some strength, or comfort, or meaning, from that urge, then God is the source of that strength, that comfort, that meaning.
"What difference? We perceive – we inhabit – one arrangement of the set of events. But why should that arrangement be unique? There’s no reason to believe that the pattern we’ve found is the only coherent way of ordering the dust. There must be billions of other universes coexisting with us, made of the very same stuff – just differently arranged. If I can perceive events thousands of kilometers and hundreds of seconds apart to be side-by-side and simultaneous, there could be worlds, and creatures, built up from what we’d think of as points in space-time scattered all over the galaxy, all over the universe. We’re one possible solution to a giant cosmic anagram … but it would be ludicrous to believe that we’re the only one."