Yesterday while watching my niece I noticed the big difference between adults and children: children are smarter. Okay more seriously, children are constantly moving around, carrying stuff here and there, doing seemingly nothing but in a very determined manner. They want to change the world and they do it. In contrast adults sit at desks and do what they are told. Then they go to theme parks and stand in lines.
Children live in a sandbox world. Or at least they see it as such and try to live it as such. They explore and learn and change what they can.
Then they grow up and just go along for the ride.
Early on, children lack the concept of object permanence. It is literally out of sight, out of mind. Then they recognize that perception is not reality, so unseen objects can still exist* and go on to become obnoxious philosophers. Eventually they reach another stage of learning: object superpermanence, in which dead NPCs respawn within minutes or seconds and they have an urgent desire to get something done and are in a big rush to get there, but they aren't quite sure what. This final state is the equivalent of Alzheimer's.
Clear proof of God: we can't see Him.