"When we talk about free will, commonly, often what's meant is the sense that 'I could have done otherwise,'" Dr. Schall said. "In the legal sense, you're responsible for shooting that guy because you could have done otherwise."
But at the level of individual nerve cells and molecules, does the picture change?
"If you push this far enough, you can't say you could have done otherwise," he said. Even though it's clear that people make choices, he said, "the kind of free will that people commonly think they want, is something that—if we're being rigorous and scientific—is unavailable to us."