Consciousness matters to us. Many would say it matters more than anything. We relish the beauty of a winter sunset, the memory-fueled comforts of a homecoming, the inviting caress of a lover's hand. Conscious sensations lie at the core of our being. Without access to this marvel, we'd be poorer creatures living in a duller world. Yet the fundamental nature of consciousness remains a scientific mystery. The problem is not that we do not understand consciousness at all—some aspects of it are relatively easy to explain. The problem is that one aspect of it continues to baffle everyone, and that's the “feel” or “phenomenal character” of consciousness—or, as philosopher Thomas Nagel has put it, simply “what it is like.” Biologist H. Allen Orr probably speaks for most scientists when, in a recent review of Nagel's book Mind and Cosmos, he writes: “I ... share Nagel's sense of mystery here. Brains and neurons obviously have everything to do with consciousness, but how such mere objects can give rise to the eerily different phenomenon of subjective experience seems utterly incomprehensible.”