Now, about 20 years ago, all that began to change. Neuroscientists like Francis Crick and physicists like Roger Penrose said now is the time for science to attack consciousness. And since then, there's been a real explosion, a flowering of scientific work on consciousness. And this work has been wonderful. It's been great. But it also has some fundamental limitations so far. The centerpiece of the science of consciousness in recent years has been the search for correlations, correlations between certain areas of the brain and certain states of consciousness. We saw some of this kind of work from Nancy Kanwisher and the wonderful work she presented just a few minutes ago. Now we understand much better, for example, the kinds of brain areas that go along with the conscious experience of seeing faces or of feeling pain or of feeling happy. But this is still a science of correlations. It's not a science of explanations. We know that these brain areas go along with certain kinds of conscious experience, but we don't know why they do. I like to put this by saying that this kind of work from neuroscience is answering some of the questions we want answered about consciousness, the questions about what certain brain areas do and what they correlate with. But in a certain sense, those are the easy problems. No knock on the neuroscientists. There are no truly easy problems with consciousness. But it doesn't address the real mystery at the core of this subject: why is it that all that physical processing in a brain should be accompanied by consciousness at all? Why is there this inner subjective movie? Right now, we don't really have a bead on that.