The major mysteries of the mind have to do with consciousness. One mystery is the relation between consciousness and its physical basis in the brain. No one has ever suggested a satisfying answer to the question of why the neural basis of a specific conscious quality, such as the experience of red, is the neural basis of that quality rather than some other quality, such as the experience of green, or of no quality at all. This mystery has been called the "hard" problem of consciousness, as contrasted with the "easy" problems of perceptual categorization, working memory, decision-making and other cognitive processes. A second mystery of consciousness has to do with how we can go about ascribing consciousness to creatures that are physically very different from ourselves. Can conscious states have a material basis very different from ours, and how would we tell? How could we know whether, for example, an intelligent machine is conscious? A third mystery is how we can investigate consciousness independently of our cognitive access to it. For example, can we know whether the representations inside a Chomskyan or Fodorian module are conscious or not? We cannot answer this question by eliciting subjects' reports, since a subject cannot report a cognitively inaccessible state. But what other type of data is there? These questions will be approached from the point of view of philosophy, neuroscience, psychoanalysis, mental illness and theology.

Gianfranco Basti is Professor of Philosophy of Nature and Science at the Pontifical Lateran University and Director of the Vatican project STOQ, or Science, Theology and Ontological Quest.

Ned Block is Silver Professor of Philosophy and Psychology at NYU. He is a former Guggenheim Fellow and a Fellow of the American Academy of Arts and Sciences. He is Co-Editor of The Nature of Consciousness: Philosophical Debates.

Richard Haier is Professor of Psychology at the University of California, Irvine (School of Medicine). He has used brain imaging with PET and MRI for the last twenty years to study intelligence. His most speculative work using brain imaging suggests a neurobiological basis for consciousness and a possible link to the neurobiological basis of intelligence.

Joseph LeDoux is University Professor and Henry and Lucy Moses Professor of Science in the Center for Neural Science and the Department of Psychology at New York University. He is Director of the NMH Conte Center for the Neuroscience of Fear and Anxiety and the author of The Emotional Brain: The Mysterious Underpinnings of Emotional Life and Synaptic Self: How Our Brains Become Who We Are.

Patrick McGrath is a novelist whose work touches on the subject of mental illness. He is the author of The Grotesque, Spider, Asylum, Martha Peake, and Port Mungo.

Craig Piers (moderator) is a psychotherapist and Clinical Supervisor in the health center at Williams College. He is former senior staff psychologist at the Austen Riggs Center and Contributing Editor of Psychoanalytic Dialogues.