Mindscan

We transferred from the spaceplane to the moonship, a metallic arachnid designed only for use in vacuum. I had my own small sleeping compartment — like one of those coffin hotels in Tokyo. When I was out of it, I was enjoying being weightless, although Quentin was still nattering on about moonbuses and other things that interested him. If only he were a baseball fan…

"Now, remember, folks," said one of the Immortex staff on the third morning of our flight, "the moonbase we're about to land at is not High Eden. Rather, it's a multinational private-sector R D facility. It wasn't built for tourists, and it wasn't built for luxury — so don't be disappointed. I promise you, you'll be pleased when you get to High Eden."

I listened, thinking High Eden indeed better be good. Of course, I'd taken the virtual tour, and read all the literature. But I'd miss — hell, I already was missing — Clamhead, and Rebecca, and my mother, and…

And, yes, even my father. I'd thought him a burden, I thought I'd feel relief to hand off worrying about him to the other me, but I found myself very sad at the prospect of never seeing him again.

Tears float in zero-gravity. It's the most astonishing thing.

I went to see Dr. Porter about the problem with thoughts I intended to keep private being spoken aloud.

"Ah, yes," he said, nodding. "I've seen that before. I can make some adjustments, but it's a tricky mind-body interface problem."

"You've got to fix it. Unless I explicitly decide to do something, it shouldn't happen."

"Ah," said Porter, his eyebrows working with glee, "but that's not how humans work — not even biological ones. None of us consciously initiate our actions."

I shook my head. "I've studied philosophy, doc. I'm not prepared to give up on the notion of free will. I refuse to believe that we live in a deterministic universe."

"Oh, indeed," said Porter. "That's not what I meant. Say you walk into a room, see someone you know, and decide to extend your hand in greeting. Of course, your hand doesn't instantly shoot out; first, stuff has to happen in your brain, right? And that stuff — the electrical change in the brain that precedes voluntary action — is called the readiness potential. Well, in a biological brain the readiness potential begins 550 milliseconds — just over half a second — prior to your hand beginning to move. It really doesn't matter what the voluntary act is: the readiness potential occurs in the brain 550 milliseconds before the motor act begins. Okay?"

"Okay," I said.

"Ah, but it's not okay! See, if you ask people to indicate exactly when they decided to do something, they report that the idea occurred to them about 350 milliseconds before the motor act begins. A guy named Benjamin Libet proved that ages ago."

"But — but that must be a measurement error," I said. "I mean, you're talking about milliseconds."

"No, not really. The difference between 550 milliseconds and 350 milliseconds is a fifth of a second: that's quite a significant amount of time, and easy enough to measure accurately. This basic test has been replicated over again over again since the 1980s, and the data are rock solid."

"But that doesn't make sense. You're saying—"

"I'm saying that what our intuition tells us the sequence of events should be, and what the sequence actually is, don't agree. Intuitively, we think the sequence must be: first, you decide to shake hands with your old friend Bob; second, your brain, in response to that decision, begins sending signals to your arm that it wants to shake hands; and third, your arm starts to swing up for the handshake. Right? But what really happens is this: first, your brain starts sending signals to shake hands; second, you consciously decide to shake hands with your old friend; and third, your arm starts to swing up. The brain has started down the road to shaking hands before you have consciously made any decision. Your conscious brain takes ownership of the action, and fools itself into thinking it started the action, but really it's just a spectator, watching what your body is doing."

"So you are saying there's no free will."

"Not quite. Our conscious minds have the free will to veto the action. See? The action begins 550 milliseconds prior to the first physical movement. Two hundred milliseconds later, the action that's already been started comes to the attention of your conscious self — and your conscious self has 350 milliseconds to put on the brakes before anything happens. The conscious brain doesn't initiate so-called voluntary acts, although it can step in and stop them."

"Really?" I said.