Just on "proof" and "evidence", one of my acquaintances is a kind of entrepreneur who flies around the world making business deals. Yes he does collect hard data to make decisions, but he also talks to taxi drivers, eavesdrops on conversations in cafes and generally talks to everyone and anyone to get a feel for the zeitgeist when considering, for example, a venture in a new country. And he often flies by the seat of his pants. If he had waited for peer-reviewed evidence that his efforts would make him rich, he'd still be waiting instead of smoking expensive cigars.