06
past which light is mostly absorbed by the medium you are looking
07
through— is tens of meters through clear water, while in air it’s practically
08
infinite. (We have no trouble seeing the moon, or distant objects on our
09
horizon.)
10
What you can see has a dramatic effect on how you think. If you’re a
11
fish, you move through the water at a meter or two per second, and you see
12
some tens of meters in front of you. Every few seconds you are entering a
13
new perceptual environment. As something new looms into your view, you
14
have only a very brief amount of time in which to evaluate how to react to
15
it. Is it friendly, fearsome, or foodlike?
16
Under those conditions, there is enormous evolutionary pressure to
17
think fast. See something, respond almost immediately. A fish brain is
18
going to be optimized to do just that. Quick reaction, not leisurely contem-
19
plation, is the name of the game.
20
Now imagine you’ve climbed up onto land. Suddenly your sensory ho-
21
rizon expands enormously. Surrounded by clear air, you can see for
22
kilometers— much farther than you can travel in a couple of seconds. At
23
first, there wasn’t much to see, since there weren’t any other animals up
24
there with you. But there is food of different varieties, obstacles like rocks
25
and trees, not to mention the occasional geological eruption. And before
26
you know it, you are joined by other kinds of locomotive creatures. Some
27
friendly, some tasty, some simply to be avoided.
28
Now the selection pressures have shifted dramatically. Being simple-
29
minded and reactive might be okay in some circumstances, but it’s not the
30
best strategy on land. When you can see what’s coming long before you are
31
forced to react, you have the time to contemplate different possible actions,
32
and weigh the pros and cons of each. You can even be ingenious, putting
33
some of your cognitive resources into inventing plans of action other than
34
those that are immediately obvious.
35S
Out in the clear air, it pays to use your imagination.
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•
01
02
Bioengineer Malcolm MacIver has suggested that the flapping of fish up
03
onto dry land was one of several crucial transitions that led to the develop-
04
ment of the thing we now call consciousness. Consciousness is not a single
05
brain organ or even a single activity; it’s a complex interplay of many pro-
06
cesses acting on multiple levels. It involves wakefulness, receiving and re-
07
sponding to sensory inputs, imagination, inner experience, and volition.
08
Neuroscience and psychology have learned a great deal about what con-
09
sciousness is and how it functions, but we are still far away from any sort of
10
complete understanding.
11
Consciousness is also a unique and heavy burden. Being able to reflect
12
on ourselves, our past and possible futures, and the state of the world and
13
the cosmos brings great benefits, but it also opens the door to alienation
14
and anxiety. The American cultural anthropologist Ernest Becker, com-
15
menting on Danish philosopher Søren Kierkegaard, once characterized
16
consciousness this way:
17
18
What does it mean to be a self- conscious animal? The idea is
19
ludicrous, if it is not monstrous. It means to know that one is
20
food for worms. This is the terror: to have emerged from noth-
21
ing, to have a name, consciousness of self, deep inner feelings,
22
and excruciating inner yearning for life and self- expression—
23
and with all this yet to die.
24
25
The special feature of self- awareness, the ability to have a rich inner life
26
and reflect on one’s place in the universe, seems to demand a special kind of
27
explanation, a unique place in the big picture. Is consciousness “just” a way
28
of talking about the behavior of certain kinds of collections of atoms, obey-
29
ing the laws of physics? Or is there something definitively new about it—
30
either an entirely new kind of substance, as René Descartes would have had
31
it, or at least a separate kind of property over and above the merely material?
32
If there is any one aspect of reality that causes people to doubt a purely
33
physical and naturalist conception of the world, it’s the existence of con-
34
sciousness. And it can be hard to persuade the skeptics, since even the most
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01
optimistic neuroscientist doesn’t claim to have a complete and comprehen-
02
sive theory of consciousness. Rather, what we have is an expectation that
03
when we do achieve such an understanding, it will be one that is completely
04
compatible with the basic tenets of the Core Theory— part of physical real-
05
ity, not apart from it.
06
Why should there be any such expectation? In part it comes down to
07
Bayesian reasoning about our credences. The idea of a unified physical
08
world has been enormously successful in many contexts, and there is every
09
reason to think that it will be able to account for consciousness as well. But
10
we can also put forward a positive case that the alternatives don’t work very
11
well. If it’s not easy to see how consciousness can be smoothly incorporated
12
as part of physical reality, it’s even harder to imagine how it could be any-
13
thing else. Our main goal here is not to explain how consciousness does
14
work, but to illustrate that it can work in a world governed by impersonal
15
laws of nature.
16
In this chapter and the next we’ll highlight some of the features of con-
17
sciousness that make it special. Then over the following few chapter
s we’ll
18
examine some arguments that, whatever consciousness is, it has to be more
19
than simply a way of talking about ordinary matter in motion, obeying the
20
conventional laws of physics. What we’ll find is that none of those argu-
21
ments is very persuasive, and we’ll be left with a greater conviction than we
22
started with that we human beings are part and parcel of the natural world,
23
thoughts and emotions and all.
24
•
25
26
Sometimes when we think about our conscious selves, we can’t help but
27
imagine a little person inside our heads, making decisions and pulling
28
strings. Even if we don’t go as far as Descartes’s belief in an immaterial soul
29
that somehow interacts with our body, it’s tempting to visualize a dictato-
30
rial “self” inside our brain that is the locus of our self- awareness. Philoso-
31
pher Daniel Dennett coined the term “Cartesian theater” to describe the
32
supposed mental control room containing a tiny homunculus who gathers
33
all of the input from our sensory organs, accesses our memories, and sends
34
out instructions to the various parts of our bodies.
35S
Consciousness doesn’t seem to be like that. Our minds are not run as
36N
top- down dictatorships; they are rambunctious parliaments, populated by
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squabbling factions and caucuses, with much more going on beneath the
01
surface than our conscious awareness ever accesses.
02
The fanciful Pixar movie Inside Out represents the process of thinking
03
as arising from a kind of teamwork between five personified emotions: Joy,
04
Sadness, Disgust, Anger, and Fear. Each of the five would offer their opin-
05
ions about the appropriate way of dealing with any particular situation, and
06
one voice would hold sway depending on the circumstances. As profes-
07
sional killjoy neuroscientists were quick to point out, that’s not actually
08
how the mind works either. But it’s a lot closer in spirit to what really hap-
09
pens than imagining a single unified self; there really are different “voices”
10
that contribute to the ultimate narrative of our conscious awareness and
11
decision making.
12
We could bring the Inside Out model closer to reality with two modifi-
13
cations. First, the various “modules” that contribute to our thought pro-
14
cesses don’t map directly onto emotions. (Neither do they have charming
15
personalities or colorful anthropomorphic bodies.) They are unconscious
16
processes of various sorts— the kind of mental functions that could have
17
naturally arisen over the course of biological evolution, well before the ex-
18
plicit development of consciousness. Second, while there is no dictator in
19
the mind, there does seem to be a kind of prime minister of the parliament,
20
a seat of cognition where the inputs from many modules are sewn together
21
into a continuum of consciousness.
22
Daniel Kahneman, a psychologist who won the Nobel Prize in Econom-
23
ics for his work on decision making, has popularized dividing how we
24
think into two modes of thought, dubbed System 1 and System 2. (The terms 25
were originally introduced by Keith Stanovich and Richard West.) System
26
1 includes all the various modules churning away below the surface of our
27
conscious awareness. It is automatic, “fast,” intuitive thinking, driven by
28
unconscious reactions and heuristics— rough- and- ready strategies shaped
29
by prior experience. When you manage to make your coffee in the morning
30
or drive from home to work without really paying attention to what you are
31
doing, it’s System 1 that is in charge. System 2 is our conscious, “slow,” ratio-
32
nal mode of thinking. It demands attention; when you’re concentrating on
33
a hard math problem, that’s System 2’s job.
34
As we go through the day, the vast majority of work being done in our
S35
brain belongs to System 1, despite our natural tendency to give credit to our
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01
self- aware System 2. Kahneman compares System 2 to “a supporting char-
02
acter who believes herself to be the lead actor and often has little idea of
03
what’s going on.” Or in the words of neuroscientist David Eagleman, “Your
04
consciousness is like a tiny stowaway on a transatlantic steamship, taking
05
credit for the journey without acknowledging the massive engineering un-
06
derfoot.”
07
The System 1/ System 2 distinction is an example of what’s known as a
08
dual process theory of thinking. An early example of such a theory was dis-
09
cussed by Plato, who in his dialogue Phaedrus introduced the allegory of
10
the chariot. He was discussing the soul, not the mind, but the ideas are
11
closely related. In the dialogue, Socrates explains that the soul has a chari-
12
oteer (System 2), and is pulled by two horses (System 1), one of which is
13
noble and the other is troublesome. Psychologist Jonathan Haidt has ar-
14
gued that Plato gives too much credit to the charioteer, and that a better
15
metaphor would be a small rider atop a giant elephant. The rider— our con-
16
scious self— exerts some control, but the majority of the power resides in
17
the elephant beneath.
18
•
19
20
The hallmark of consciousness is an inner mental experience. A dictionary
21
definition might be something like “an awareness of one’s self, thoughts,
22
and environment.” The key is awareness: you exist, and the chair you’re sit-
23
ting on exists, but you know you exist, while your chair presumably does
24
not. It’s this reflexive property— the mind thinking about itself— that
25
makes consciousness so special. MacIver suggests that one of the most im-
26
portant pieces in this puzzle— the ability to take time to contemplate mul-
27
tiple alternatives, breaking the immediate connection between stimulus
28
and response— started to become selected for by evolution once we crawled
29
up onto the rocks.
30
It is natural to suppose that our imaginative faculties grew out of the
31
evolutionary pressure in favor of developing the ability to weigh competing
32
options for our future actions. Psychologist Bruce Bridgeman has gone so
33
far as to characterize consciousness as “the operation of the plan- executing
34
mechanism, enabling behavior to be driven by plans rather than immediate
35S
environmental contingencies.” Consciousness is more than that; we can be
36N
conscious of being in love or enjoying a symphony without necessarily
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making associated plans. But the ability to conjure different hypothetical
01
futures is certainly part of it.
02
There’s a lot going on beneath the deceptively simple idea of “making
03
plans.” We have to have the ability to conceive of times in the future, not
04
merely the present moment. We need to be able to represent the actions of
05
both ourselves and the rest of the world in our mental pictures. We must
06
reliably predict future actions and their likely responses. Finally, we must
07
be able to do this for multiple scenarios simultaneously, and eventually
08
compare and choose between them.
09
The ability to plan ahead seems so basic that we take it for granted, but
10
it’s quite a marvelous capacity of the human mind.
11
12
•
13
The “now” of your conscious perception is not the same as the current mo-
14
ment in which you are living. Though we sometimes think of consciousness
15
as a unified essence guiding our thoughts and behavior, in fact it is stitched
16
together out of inputs from different parts of the brain as well as our sen-
17
sory perceptions. That stitching takes time. If you use one hand to touch
18
your nose, and the other to touch one of your feet, you experience them as
19
simultaneous, even though it takes longer for the nerve impulses to travel
20
to your brain from your feet than from your nose. Your brain waits until all
21
of the relevant inputs have been assembled, and only then presents them to
The Big Picture Page 54