Tim Bayne, Philosophy of Religion: A Very Short Introduction (Oxford University Press, 2018), 37-38.
Let us grant then that the fine-tuning facts require explanation. Can science provide the necessary explanation? Many physicists and philosophers argue that it can. The most influential response here appeals to the ‘many worlds’ or ‘multiverse’ hypothesis. The basic idea is this. The existence of a finely tuned world would be surprising given the assumption that there is only one universe, but it may not be surprising if our universe is only one of a vast (perhaps infinite) number of universes, each of which exhibits variation in the values of the basic physical constants. If the multiverse hypothesis were correct, then – this line of thought continues – we would have a purely scientific explanation for the fine-tuning facts. Although the vast majority of universes fail to support life, occasionally the fundamental constants are such that intelligent life becomes possible. Our world just happens to be such a world. We might liken the multiverse scenario to a scenario in which the expert marksmen don’t shoot just one prisoner, but fire at a vast (perhaps infinite) number of prisoners. In such a scenario, one might expect that although the vast majority of prisoners will die, occasionally someone survives, and of course it’s only the survivors who are in a position to reflect on their luck.