The human brain is an organ out of time. It stands as evolved and best suited for daily life in the Pleistocene yet here it is, having to make do in a modern, high-tech, wired, and fast-changing world.

We have magnificent brains—and use them to believe nonsense and behave as fools. . . . We are enslaved to delusions and too often the servants of subconscious biases. . . . Our great challenge is to use our brains to overcome our brains.

In attempting to know, we engage in grand and meaningful acts. We use our human brains as time machines, to see and learn from the distant past and to travel forward thousands, millions, and billions of years. This young, patchwork organ that evolved to help ancient primates find food and water, maintain group relationships, achieve sexual intercourse, and imagine the next best tool now carries us to the very ends of the universe and beyond.

Critical thinking is the indispensable skill for smart living in modern society, and skepticism is the essential posture for the fully awake twenty-first-century human being.