The prudent leader “dreads and reflects on everything that can happen to him but is bold when he is in the thick of action.” Xerxes listens patiently, but objects that “if you were to take account of everything . . . , you would never do anything. It is better to have a brave heart and endure one half of the terrors we dread than to [calculate] all

Merkel is firm, clear, and patient. She’s willing to compromise on everything except the principle at stake—which far too many people lose sight of.

because their causes were knowable, their consequences were predictable. But only individually, for not even the canniest seer can specify cumulative effects. Little things add up in unpredictably big ways—and yet, leaders can’t let uncertainties paralyze them. They must appear to know what they’re doing, even when they don’t.