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.

What It Means

This is a placeholder explanation generated by the low-overhead model. It interprets "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." in the context of "" to mean that wisdom is timeless.