Enlightenment Now: The Case for Reason, Science, Humanism, and Progress

The other supposedly God-fillable gap is the “hard problem of consciousness,” also known as the problem of sentience, subjectivity, phenomenal consciousness, and qualia (the “qualitative” aspect of consciousness).³⁹ The term, originally suggested by the philosopher David Chalmers, is an in-joke, because the so-called easy problem—the scientific challenge of distinguishing conscious from unconscious mental computation, identifying its substrates in the brain, and explaining why it evolved—is “easy” in the sense that curing cancer or sending a man to the Moon is easy, namely that it is scientifically tractable. Fortunately, the easy problem is more than just tractable: we are well on the way to a satisfying explanation. It’s hardly a mystery why we experience a world of stable, solid, colored 3-D objects rather than the kaleidoscope of pixels on our retinas, or why we enjoy (and hence seek) food, sex, and bodily integrity while suffering from (and hence avoiding) social isolation and tissue damage: these internal states and the behavior they encourage are obvious Darwinian adaptations. With advances in evolutionary psychology, more and more of our conscious experiences are being explained in this way, including our intellectual obsessions, moral emotions, and aesthetic reactions.⁴⁰

Nor are the computational and neurobiological bases of consciousness obstinately befuddling. The cognitive neuroscientist Stanislas Dehaene and his collaborators have argued that consciousness functions as a “global workspace” or “blackboard” representation.⁴¹ The blackboard metaphor refers to the way that a diverse set of computational modules can post their results in a common format that all the other modules can “see.” Those modules include perception, memory, motivation, language understanding, and action planning, and the fact that they can all access a common pool of currently relevant information (the contents of consciousness) allows us to describe, grasp, or approach what we see, to respond to what other people say or do, and to remember and plan depending on what we want and what we know. (The computations inside each module, in contrast, like the calculation of depth from the two eyes or the sequencing of muscle contractions making up an action, can work off their own proprietary input streams, and they proceed below the level of consciousness, having no need for its synoptic view.) This global workspace is implemented in the brain as rhythmic, synchronized firing in neural networks that link the prefrontal and parietal cerebral cortexes with each other and with brain areas that feed them perceptual, mnemonic, and motivational signals.

The so-called hard problem—why it subjectively feels like something to each one of us who is conscious, with red looking red and salt tasting salty—is hard not because it is a recalcitrant scientific topic but because it is a head-scratching conceptual enigma. It includes brainteasers such as whether my red is the same as your red, what it is like to be a bat, whether there could be zombies (people indistinguishable from you and me but with “no one home” who is feeling anything), and if so whether everyone but me is a zombie, whether a perfectly lifelike robot would be conscious, whether I could achieve immortality by uploading my brain’s connectome to the Cloud, and whether the Star Trek transporter really transports Captain Kirk to the planetary surface or murders him and reconstitutes a twin.

Some philosophers, like Daniel Dennett in Consciousness Explained, have argued that there is no hard problem of consciousness: it is a confusion arising from the bad habit of imagining a homunculus seated in a theater inside the skull. This is the disembodied experiencer who would temporarily tiptoe out of my theater and drop in on yours to check out the red, or visit the bat’s and watch the movie that’s playing there; who would be missing from the zombie and either present or absent in the robot; and who might or might not survive the beam ride down to Zakdorn. Sometimes, when I see the mischief that the hard problem has caused (including the conservative intellectual Dinesh D’Souza brandishing a copy of my book How the Mind Works in a debate on the existence of God), I am tempted to agree with Dennett that we’d be better off without the term. Contrary to various misunderstandings, the hard problem does not consist in weird physical or paranormal phenomena such as clairvoyance, telepathy, time travel, augury, or action at a distance. It does not call for exotic quantum physics, kitschy energy vibrations, or other New Age flimflam. Most important for the present discussion, it does not implicate an immaterial soul. Nothing that we know about consciousness is inconsistent with the understanding that it depends entirely on neural activity.