Yeah, and we have a case. We're trying to develop a fictional world. You can't expect that to be accomplished in any reasonable way by fiddling over crazy high level stuff like whether or not the world has magic for weeks at a time. Throw the ideas out there, let people mull them over, then toss in some details. The details will mold the high level stuff around them and it'll work out.

World building from the outside in may work for some people, but frankly it doesn't make any sense to me. Build it the way you want your players to see it, from the inside out. Your players are going to be individual characters, and if you don't have a personalized sense of the world your characters are living in then it doesn't matter how mechanically accurate rivers or climates are, or whether it makes sense from an astronomical perspective if the planet has one moon or five. Your players really don't give a damn. They just want something fun, relate-able and interesting. And you're not getting anywhere near that if you don't even have a remote sense of what the people who actually live in this world are like.