“It’s easy, today, to chuckle at Aristotle’s error. But it’s also easy to understand how the great philosopher was led so far astray. The brain, packed neatly into the bone-crate of the skull, gives us no sensory signal of its existence. We feel our heart beat, our lungs expand, our stomach churn—but our brain, lacking motility and having no sensory nerve endings, remains imperceptible to us. The source of consciousness lies beyond the grasp of consciousness.”