People who don’t believe in relativity don’t understand relativity. People who don’t believe in evolution… — Jonathan Weiner

Philosophers used to ask whether we are born with or invent our sense of time. Now we know that we have clocks woven into every one of our cells. Philosophers also used to ask how we know that the sun will rise tomorrow. In a sense we have that answer built into us, too. The clock is a kind of orrery in the heart of every one of our cells, revolving to help us keep time with our world, a model of the cosmos inside our heads that cycles whether we are in or out of sight of the sun. The revolution of the stars and the seasons is written in the turns of our DNA.

“Ethicists are a mixed lot,” he says, “generally not worrying about their own problems, just somebody else’s problems.”

Watson sighs. “So in that sense you don’t have a free will. Your reactions are programmed. You know, you start asking the difference,” he says with a nod toward the Fly Room next door. “What free will is there in Drosophila? You put the question of the free will of a fly. And what’s really different about the fly’s brain from ours—which gives us free will?

“I’m sure once we know how the brain works, we’ll no longer talk about free will in the Jesuit sense. It will cease to be, you know—” Freedom will cease to be a mystery requiring Jesuitical debate; it will cease to be a theological or philosophical question. “It will just be how the brain works. You will describe how the brain works. You won’t use the words ‘free will’; you know, you’ll understand…. Because you’re asking, how does the brain work?” He says in a softer voice. “That’s what you’re really asking.” The bell in the double-helical bell tower outside his office window begins to toll. “And that’s really the ultimate question to ask,” he says.