I recently picked up a copy of Billions & Billions by the late Carl Sagan. I'm a big fan of him, with his series Cosmos being rather influential in my choice of area of study at university. In a chapter entitled Four Cosmic Questions, he suggests that most creation myths were written by storytellers (fine so far as it goes), but that the creation myth that science gives us is "based on hard scientific evidence." Again, so far, so good. After a very brief summary of the big bang he notes that some scientists believe in a multiverse - an infinitity of universes.
Hang on, isn't he supposed to be writing about things based on hard science? Where is the hard science for a multiverse? There is quantum mechanics which could allow such things, but where is the proof. Perhaps the statement about some scientists should be enough. However, in denouncing creation myths as made up stories in contradistinction to scientific accounts, he has slipped metaphysics in under the radar.
Let's be clear - most creation stories are made up, attempts to try and explain the world. But what if a god really exists? What then? The multiverse nicely removes the need for a creator. It only holds if we already know for certain no such being exists, and if there is evidence for multiverses. The former is mere assumption, the later doesn't (currently) exist. Nice try Dr Sagan.