Physicist Paul Davies, from the conclusion of his book, The Goldilock’s Enigma:
So, how come existence? At the end of the day, all the approaches I have discussed are likely to prove unsatisfactory. In fact, in reviewing them they all seem to me to be either ridiculous or hopelessly inadequate: a unique universe which just happens to permit life by a fluke; a stupendous number of alternative parallel universes which exist for no reason; a pre-existing God who is somehow self-explanatory; or a self-creating, self-explaining, self-understanding universe-with observers, entailing backward causation and teleology. Perhaps we have reached a fundamental impasse dictated by the limitations of the human intellect.