Well, I don’t think it’s possible to prove the existence of God. There are many things I don’t think you can prove in an absolutely cast-iron, logical way. You can prove that two plus two equals four; you can’t prove the foolishness or falseness of ridiculous assumptions. I could maintain that the whole world came into existence five minutes ago and that our memories of the past were created at that moment. I don’t think you could defeat me in logical argument about that, though we all know that would be an absurd thing to say. So proof, cast-iron proof, is pretty limited and not actually a very interesting category of things. I believe in quarks and gluons and electrons. I believe that’s the most intelligible, economic, persuasive interpretation of a whole swath of physical phenomena, but I don’t think I’ve proved their existence in the two plus two equals four sense — just as I can’t prove the existence of God. What we need, I think, is beliefs that are sufficiently well-motivated for us to feel that we can commit our lives to them, knowing that they may be false, but believing that they are the best explanation. I’m very sold on motivated belief but I am not sold on knowledge through proofs either in science or religion, or anything in between.
Mental multivitamin: John Polkinghorne: "I call myself a bottom-up thinker."