When you have an object such as the human brain, which is the most complex lump of matter in the known universe, there is a good chance that various emergent properties will materialize there as well. I’m not for one moment proposing Descartes’ immaterial ghost, and shudder at its unscientific and religious connotations. But within a scientific, physical-based framework, I endorse and will discuss the idea that the brain is much more than the sum of its parts, and that consciousness may be its most shining, fascinating product.
THE IMPENETRABILITY OF “WHAT IT IS LIKE”
By the middle of the twentieth century, philosophy had largely caught up with neuroscience in believing that the mind was equal to the brain, and that any thought or feeling was really a collection of brain cells firing away. In fact, with the advent of computers, and the acknowledgment that we were nothing more than biological machines, the equation of mind with brain soon mutated into the equation of mind with computer program. We happened, by the quirks of evolution, to have been lumbered with this particularly wrinkly, jelly-like computer to substantiate the program of our minds, but it didn’t have to be this way; we could, in principle, have just the same thoughts with a “brain” made of silicon chips.
This theory of “mind as a computer, which accidentally equals brain,” is the most widely discussed philosophical position about the mind held today. It is also the view that almost all neuroscientists assume by default. But that hasn’t stopped some modern philosophers from attacking it from almost every angle.
The first doubt comes from the suggestion that the mind can be entirely reduced to the brain (or computer, or whatever other physical object one would care to mention). Descartes opposed the possibility of this reduction, assuming that there was something intrinsically subjective and nonphysical about the mental world. In 1974, Thomas Nagel, in one of the most famous philosophy papers of the past hundred years (“What Is It Like to Be a Bat?”), echoed Descartes’ position in modern form. Nagel accepted that thoughts could be characterized according to their ability to cause other thoughts and behavior, and he was certainly not opposed outright to the idea that minds were simply brains. But he did think there could be a problem with this view. If you and I hear Shostakovich’s
Tenth Symphony
, I can make a great stab at imagining what it was like for you to hear the music. Of course, I may be entirely wrong in my imagination, but I can at least generate a plausible guess as to what you experienced. I might even have a good go at imagining what my cat experiences when she hears the doorbell ring. We have similar ears mechanistically, and our brains’ primary hearing centers also aren’t entirely dissimilar. But if I try to imagine what a bat “see/ hears” when it uses echolocation to navigate, then I have no idea where to begin. Assuming that a bat is conscious, then our two consciousnesses seem totally incompatible. I can gain absolutely no knowledge about bat consciousness—at least not in the realm of echolocation.
2
And if I can’t even imagine what it is like to sense with echolocation, what hope is there that I can get a foothold using any of science’s tools?
This “what is it like” aspect of thought, Nagel claimed, was the essence of consciousness, and it posed a problem, in particular, for those wishing to reduce consciousness to a physical process in the brain. Nagel believed that if some animal was conscious, then it had to have a “what is it like?” aspect to it. Nagel did not state that it was impossible for us to understand what it was like to be a bat, although he did suggest that this barrier was a fundamental problem for science, one that it had to face with radically different, novel approaches.
Australian philosopher Frank Jackson took this position one step further and argued that it actually
is
impossible for science to explain mental states using only physical processes. His argument revolved around a thought experiment, which went something like the following.
Imagine that the year is 2412 and evil philosophers control the planet. One small coven of hellish thinkers calling themselves the Descartes Brigade hatches an idea for a cruel but potent experiment. The most celebrated scientist husband and wife in the world have just given birth to a beautiful daughter called Mary, but at the precise moment she’s born, the Descartes Brigade kidnaps her and locks her up in a windowless black and white room. They bleach her skin white, and even cosmetically alter her irises to be black, along with her hair. They feed her black and white foods through a small black hatch in the white wall, and as she grows up they entertain and teach her on black and white laptops and monitors. The physical sciences have been completed by this stage, and it is possible to know everything about physics, chemistry, and biology, especially including the brain sciences. Mary has little else to do, and anyway, like her parents, she has an aptitude for and love of science, so she takes it upon herself to learn this completed science. By the age of thirty, after decades of diligent study, she knows absolutely everything about the physical world (stupendously implausible, of course, but let’s for the moment assume it’s possible), from the nature of all the subatomic particles to the activity of every brain cell that represents color vision in humans. The members of the Descartes Brigade at this stage know that their plan is coming to fruition and, finally, they unlock the door to Mary’s prison, letting her wander outside for the first time in her life. Dazzled by what she sees, overwhelmed, overjoyed, she stumbles into a nearby garden and bends down to stare at a red rose. As she views the scarlet color she exclaims, in shock: “Before being released I knew every physical detail of how the brain generates consciousness, but now I know something new:
I know what it is like to see red
. This extra knowledge is something that the physical sciences could never capture. Therefore there is something
nonphysical
about consciousness!” At this stage, she collapses and suffers a terrible nervous breakdown, but the philosophers of the Descartes Brigade callously rejoice. They believe that their poor guinea pig, Mary, has helped them show that consciousness is at least partly nonphysical. The evil philosophy gang members end their pamphlet by boldly proclaiming that Descartes was right all along!
Although this argument has indeed been influential, it is not as watertight as it might at first appear. In some ways it suffers from the same problems as Descartes’ argument. Descartes made the mistake of overreaching with his level of knowledge (because he didn’t know the existence of his body with as much certainty as he knew the existence of his mind, he leaped to the conclusion that his body was distinct from his mind, even though he never actually established that this was the case). Here Jackson was similarly overreaching by making strong assumptions about what a complete physical understanding of the universe would entail. Lord Kelvin, one of the greatest physicists of the nineteenth century, is reputed to have proclaimed, as recently as 1900, that “There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.” The timing of this claim was somewhat comical: That same year, Max Planck initiated one physics revolution by introducing quantum mechanics to the world. Then, five years later, Albert Einstein followed with a set of his own revolutionary theories, including special relativity and the equivalence of energy and mass.
We have absolutely no idea what this “completed physics” will look like in four hundred years’ time. In fact, startling revolutions could turn up at any moment to thoroughly embarrass anyone clinging to scientific dogmatism. A twenty-fifth-century portrait of the universe may well be far more bizarre than superstring theory or quantum mechanics, and it would be rather pointless to speculate on the details. It would also be foolhardy in the extreme to assume with certainty, as Jackson’s argument above seems to do, that such future physical scientific wisdom could not include a complete explanation of consciousness.
Indeed, this is not the only argument that can be raised against Jackson’s thought experiment. Suppose that Mary, bunkered down in her black and white room, actually has a wistful fascination for the flora and fauna that lie just outside her philosophers’ jail. So when she’s not studying the physical properties of neuronal circuitry, her hobby involves learning about the garden just outside. She hacks into a robot in the neighborhood, which happens to have some decent cameras for eyes. She steers it to her nearby garden and by this means finds out exactly what wavelengths of light are being emitted from the rose bush over the next few days. She therefore discovers what shade of red the rose is. Just to be certain, she practices more hacking skills on some nearby twenty-fifth-century flying brain scanners, which just happen to be a popular tool of the Big Brother government of the time. By this means, she sees the brain activity of all the passersby as they glance at the roses, and she infers easily that this activity corresponds to the experience of seeing red in every case. So before Mary ever leaves the room, she has incontrovertible, highly detailed knowledge from a range of sources that the roses in the garden near her room are indeed red. It’s important to emphasize, therefore, that when Mary finally is released from her room, she doesn’t necessarily suddenly discover that the rose is red—
she could already know this
. All she actually knows now that she did not know before is “what it is like to see” red. And this is a very strange kind of knowledge indeed. So what has she actually learned, if anything? Some philosophers suspect that she has not learned any new information whatsoever.
Because of this suspicion, a few critics of Jackson’s thought experiment have argued that “knowing what it is like to see color” is really like an
ability
to gather knowledge rather than knowledge itself. (In fact, Frank Jackson himself should be included on this list, because he has since rejected his former argument, largely in favor of this idea.) Our color vision allows us to learn many useful things, such as when fruits are ripe, or, in more modern climes, to know when a traffic light indicates that we should stop the car. But this information relates to knowing
that
something is red. Knowing
what it is like
to see red is more abstract, and perhaps could best be described as
an ability to recognize red if we came across it in the future
; in other words, a rather specific ability to gather color information directly, without recourse to external machines such as cameras.
Nowadays, we have multiple ways in which to acquire color information using natural and artificial technologies, such as our eyes or a digital camera. But whether the source is our eyes or some fabulous feat of modern technology, all that really matters is that the information
is
acquired, rather than
the way
it is acquired. The information, the knowing
that
the rose is red, is independent of the tool by which that information is acquired. By contrast, “knowing what it is like” is dependent on the tool used to gather the information—in this case, Mary’s eyes. Consequently, it isn’t “knowing” at all—it is merely the ability to use the specific tool of our eyes in order to acquire knowledge. So it’s at least plausible that Mary didn’t, after all, know anything new when she was finally let out of her monochrome prison and saw the red rose. Therefore, consciousness can still be a purely physical event.
CAN A PROGRAM HAVE FEELINGS?
The other aspect of the standard model of consciousness is that it’s not only a physical process, carried out by the brain, but also a
computational one
. Modern philosophers have taken issue with this stance as well, attempting to argue that there are unique characteristics to consciousness in its natural biological form, which means we could never be converted into some silicon equivalent.
One prominent attack on the computational view of consciousness revisits the “what is it like” aspect of awareness, which includes all of our emotions and senses. The argument claims that the existence of this vital aspect of experience proves that consciousness cannot be captured by a computer. You and I both know that strawberries are red and blueberries blue, but what if my inner experiences of reds and blues are your experiences of blues and reds? Arguments along these lines assume it’s quite conceivable that we would neither behave nor think differently when faced with a fruit salad. Consequently, the software equivalent of our minds could pick any old values to represent the reds and blues—or even entirely omit this bothersome bit of code, and by extension the rest of our color vision and all other senses and emotions—without weakening the fidelity of the program. But if this defining facet of our consciousness is a mere irrelevance to its computational equivalent, then that is a step too far, and computers simply cannot represent consciousness.
However, when the scientific details are taken into account, there is something ridiculous in the idea that you can simply swap red with blue, and leave all thoughts and behavior otherwise unchanged. Our perception of something as “red” is generated not just from the wavelength our eyes pick up, but also the vividness of the color, its comparison with the surrounding colors, its brightness, the meanings and categories of colors, and so on—and all this interacts with our other senses and feelings in an incredibly complex network of information (just think of “the blues” as a form of music depicting a class of emotion). All this perfectly mirrors the architecture of the brain, which is an inordinately dense web of connectivity, such that changing one region may modify the function of many others.