Consciousness is the appearance of a world. The essence of the phenomenon
of conscious experience is that a single and unified reality becomes
present: If you are conscious, a world appears to you. This is
true in dreams as well as in the waking state, but in dreamless deep
sleep, nothing appears: The fact that there is a reality out there and that
you are present in it is unavailable to you; you do not even know that
you exist.
Consciousness is a very special phenomenon, because it is part of the
world and contains it at the same time. All our data indicate that consciousness
is part of the physical universe and is an evolving biological
phenomenon. Conscious experience, however, is much more than
physics plus biology—more than a fantastically complex, dancing pattern
of neural firing in your brain. What sets human consciousness
apart from other biologically evolved phenomena is that it makes a reality
appear within itself. It creates inwardness; the life process has become
aware of itself.
Judging from the available data on animal brains and evolutionary
continuity, the appearance of worlds in biological nervous systems is a
recent phenomenon, perhaps only a few million years old. In Darwinian
evolution, an early form of consciousness might have arisen some 200 million years ago in the primitive cerebral cortices of mammals, giving
them bodily awareness and the sense of a surrounding world and guiding
their behavior. My intuition is that birds, reptiles, and fish have long
had some sort of awareness too. In any case, an animal that cannot reason
or speak a language can certainly have transparent phenomenal
states—and that is all it takes to make a world appear in consciousness.
Such well-known consciousness researchers and theoretical neurobiologists
as Anil Seth, Bernard Baars, and D. B. Edelman have established
seventeen criteria for brain structures subserving consciousness, and
the evidence for the existence of such structures not only in mammals
but also in birds and potentially in octopi is overwhelming. The empirical
evidence for animal consciousness is now far beyond any reasonable
doubt. Like us, animals are naive realists, and if they have, say, color
sensations, it is plausible to assume that these appear to them with the
same quality of directness, certainty, and immediacy as they do to us.
But the philosophical point is that we really do not know. These are exactly
the sort of questions we can consider only after we have constructed
a satisfactory theory of consciousness.
A much more recent phenomenon emerged only a couple of thousand
years ago—the conscious formation of theories in the minds of human
philosophers and scientists. Thus the life process became reflected
not only in conscious individual organisms but also in groups of human
beings trying to understand the emergence of self-conscious minds as
such—that is, what it means that something can “appear within itself.”
The most fascinating feature of the human mind, perhaps, is not simply
that it can sometimes be conscious, or even that it allows for the emergence
of a PSM. The truly remarkable fact is that we can also attend to
the content of our PSM and form concepts about it. We can communicate
about it with one another, and we can experience this as our own
activity. The process of attending to our thoughts and emotions, to our
perceptions and bodily sensations, is itself integrated into the selfmodel.
This property, as noted, probably distinguishes us from most
other animals on this planet: the ability to turn the first-person perspective
inward, to explore our emotional states and attend to our cognitive
processes. As philosophers say, these are “higher-order” levels of the PSM. They allowed us to become aware of the fact that we are representational
systems.
Over the centuries, the theories we have devised have gradually
changed our image of ourselves, and in so doing they have subtly altered
the contents of consciousness. True, consciousness is a robust phenomenon;
it doesn’t change simply because of the opinions we have about it.
But it does change through practice (think of wine connoisseurs, perfume
designers, musical geniuses). Human beings in other historical
epochs—during the Vedic period of ancient India, say, or during the European
Middle Ages, when God was still perceived as a real and constant
presence—likely knew kinds of subjective experience almost
inaccessible to us today. Many deep forms of conscious self-experience
have become all but impossible due to philosophical enlightenment and
the rise of science and technology—at least for the many millions of
well-educated, scientifically informed people. Theories change social
practice, and practice eventually changes brains, the way we perceive
the world. Through the theory of neural networks, we have learned that
the distinction between structure and content—between the carrier of a
mental state and its meaning—is not as clear-cut as is often assumed.
Meaning does change structure, though slowly. And the structure in
turn determines our inner lives, the flow of conscious experience.
In the early 1970s, after the heyday of behaviorism, interest in consciousness
as a serious research topic began to rise. In several scientific
disciplines, the topic of subjective experience gradually became a secret
research frontier. Then, in the last decade of the twentieth century, a
number of eminent neuroscientists accepted consciousness as a proper
target for rigorous research. Now things developed very quickly. In 1994,
after a conference of consciousness researchers in Tucson, Arizona, I
helped found a new organization, the Association for the Scientific
Study of Consciousness (ASSC), which is aimed at drawing together
the more rigorous researchers in science and philosophy. The number
of conferences and journal articles increased steeply. The following
year, I edited a collection of philosophical articles entitled Conscious Experience. When one of my ASSC cofounders, Australian philosopher
David Chalmers, and I compiled the bibliography, spanning the period 1970–1995, it contained about a thousand entries. Ten years later, when I
updated this bibliography for the fifth German edition, it had almost
twenty-seven hundred entries. At this point, I gave up my attempt to include
all of the new literature on consciousness; it was simply no longer
possible. The field is now well established and developing steadily.
In the meantime, we have learned many lessons. We have learned
how great the fear of reductionism is, in the humanities as well as
among the general public, and how immense the market is for mysterianism.
The straightforward philosophical answer to the widespread fear
that philosophers or scientists will “reduce consciousness” is that reduction
is a relationship between theories, not phenomena. No serious empirical
researcher and no philosopher wants to “reduce consciousness”;
at best, one theory about how the contents of conscious experience
arose can be reduced to another theory. Our theories about phenomena
change, but the phenomena stay the same. A beautiful rainbow continues
to be a beautiful rainbow even after it has been explained in terms of
electromagnetic radiation. Adopting a primitive scientistic ideology
would be just as bad as succumbing to mysterianism. Furthermore,
most people would agree that the scientific method is not the only way
of gaining knowledge.
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