Well I'm an atheist but that shared tradition you mention is as much mine as it is yours. Those ancient cathedrals and other venerable religious sites are mine as much as they're yours. You can't claim that tradition and experience for yourself and exclude me. Therefore you and I need to work out why we have reached radically different conclusions about the nature of things. Your traditions, mythology and experience are no different to mine. So we could sideline them for a minute and resort to reason instead. We could, but we won't. That's your issue.