Why so many of us a million years ago purposely knocked out major chunks of our brains with alcohol from time… — Kurt Vonnegut

Mere opinions, in fact, were as likely to govern people's actions as hard evidence, and were subject to sudden reversals as hard evidence could never be. So the Galapagos Islands could be hell in one moment and heaven in the next, and Julius Caesar could be a statesman in one moment and a butcher in the next, and Ecuadorian paper money could be traded for food, shelter, and clothing in one moment and line the bottom of a birdcage in the next, and the universe could be created by God Almighty in one moment and by a big explosion in the next — and on and on.

That, in my opinion, was the most diabolical aspect of those old-time brains: They would tell their owners, in effect, "Here's a crazy thing we could actually do, probably, but would never do it, of course. It's just fun to think about."

And then, as though in trances, the people would really do it — have slaves fight each other to death in the Colosseum, or burn people alive in the public square for holding opinions which were locally unpopular, or build factories whose only purpose was to kill people in industrial quantities, or to blow up whole cities, and on and on.