Noam Chomsky,
Professor of Linguistics, Massachusetts
Institute of Technology, received an
honorary Doctor of Letters degree during the ceremony
The
Text:
There's no really natural transition to the topic
I would like to say a few words about, namely the prospects
for the brain and cognitive sciences, what is sometimes felt
to be the last great mountain range that the natural sciences
might hope to scale.
But there is perhaps a certain transition.
A forthcoming paper by one of the
leading researchers in cognitive neuroscience,
Randy Gallistel, argues - pretty convincingly, I think -
that a long tradition of research and speculation is seriously
off the mark in its beliefs about general learning processes
and associative theories of learning. Rather, throughout
zoology and experimental psychology it is increasingly becoming
clear that learning mechanisms are computationally
specialized behavior for solving particular kinds of problems.
That ranges from insect behavior, to shooting the winning
basket for the Celtics, to what you and I are doing right
now.
Gallistel also points out that this "modular view of earning" is "the
norm these days in neuroscience." According to this view,
in all animals learning is based on specialized mechanisms,"instincts
to learn" in specific ways. These "learning mechanisms" can
be regarded as "organs within the brain [that] are neural
circuits whose structure enables them to perform one particular
kind of computation."
They do that reflexively, unless the
environment is "extremely hostile." Human language acquisition
is instinctive in this sense, based on a specialized "language
organ," which grows from an initial state that is an expression
to the genes through various stages until it reaches a mature
state that corresponds more or less to what we informally
call "a language"; say, some variety of English.
And this
transition does appear to take place
as a virtual reflex, apart from "extremely hostile environments." It seems that
normal normal knowledge of language can be closely approximated
even by the deaf-blind, using only the extremely rudimentary
information that is provided by placing a hand on the face
of a person who is speaking, though the f ull story is somewhat
more complex.
These are the specific topics of cognitive psychology
that have been of particular interest to me for many years.
I think the work of the past half century, including ground-breaking
work that has been done right here, quite strongly supports
the general thesis that Gallistel takes to be the norm in
neuroscience: the circulatory system, the digestive system,
the kidney, the visual systems, and so on.
These are often
called "organs of the body," but of course not with the implication
that they can be removed leaving the rest intact. Rather,
these are subsystems of a complex whole, with their own specialized
properties, interacting in specific ways - organs in a useful
but somewhat abstract sense., There seems every reason to
believe that the human brain is structured along similar
lines.
Gallistel also sounds a useful warning note: he
points out that "We clearly do not understand how the nervous
system computes," even "how it carries out the small set
of arithmetic and logical operations that are fundamental
to any computation." A great deal has been learned about
several of the organs that enter into human thought and action,
notably the language organ.
But enormous gaps of understanding
remain. One of them is the gap between
theories of the nature, growth, and use of the organ, and
theories of the anatomy and psychology of the brain. It is
for such reasons that the organs that enter into thought
and action are often called "mental
organs," to signal that the problem of unification of mental
aspects of the world and other aspects, in this case, we
presume, cellular aspects.
As Gallistel notes, the problem arises for all
psychological processes. It shows up in many ways. Thus,
a great deal has been learned about vision in recent years,
but as another prominent neuroscientist recently pointed
out, the ability to recognize "a continuous vertical line
is a mystery that neurology has not yet solved." The word "yet" should
sound another warning note: no one can guess what might be
necessary even for this problem to be solved, let alone what
changes in basic science might be required to relate mental
aspects of the world to others.
Many leading figures in the brain and cognitive
sciences are optimistic about the prospects, but not without
recognizing the gaps that remain - "chasms" might be a better
word. One of the grand old men of the field, Vernon Mountcastle,
who is one of the optimists, observes that the study of higher
mental faculties raises a serious question about the validity
of "the long-standing dogma of neuroscience conserved in
mammalian evolution."
The dogma may not be "universally true," he
suggests,"especially if it applies to the human brain," which
appears to have neuron types that differ from those of other
mammals in biochemical mechanisms and patterns of connectivity.
Still more seriously, we do not even know if these are the
right mechanisms and patterns to explore in seeking to achieve
unification of mental and cellular theories of the world.
It is generally assumed that the human species
reached essentially its current state about 100,000 years
ago, after very radical changes in the preceding several
million years. These developments included a tripling of
brain size and a great many structural changes long after
the separation from the nearest surviving relatives, roughly
5 million years ago, which means a separation of twice that
length in evolutionary terms. It is also assumed that whatever
happened about 100,000 years ago probably involved the appearance
of a language organ, and with it, presumably, many of the
other distinctive properties of our curious species.
That's
a flick of an eye in evolutionary terms.
Also intriguing is the apparent biological isolation
of the human language faculty. Perhaps the closest analogues
are in insects - the famous dance of the honeybees. But there
is a good deal of controversy about
the nature and function of these systems, the analogies at
best are very weak, and there is of course no evolutionary
relation.
The basic facts were observed by Darwin, who noted
the radical distinction between human language and all known
animal systems of communication. Human language, he pointed
out, is infinite in its capacity for expression of thought,
while other animals crucially lack that property, and as
we now know, many other elementary properties of human language
as well. The observation is in fact far older: it was noted
by Galileo, and became a central part of the great scientific
revolution of the 17th century - and that included
the first great "cognitive revolution," perhaps the only
one that really merits the term.
The 17th century scientific revolution reached
its highest peak in the achievements of Isaac Newton. It is
commonly held that Newton showed that the universe is an intricate
mechanism, rather like the complex automata that captured
the imagination of 17th-18th century thinkers, much as computers
do today. But in fact what Newton demonstrated was exactly
the opposite. Newton showed, much to his dismay, that the
universe is not a mechanical device.
To quote a leading modern
historian of physics, Newton showed that "a purely materialistic
or mechanistic physics is impossible," that it is necessary
to introduce into core natural science "incomprehensible and
inexplicable facts" (Alexander Koyre).
Newton regarded his own conclusions as an "absurdity," and
spent the rest of his life trying to find some escape, as
did many other leading scientists, in fact for centuries.
But in vain.
It is common these days to ridicule those who
still believe in the ghost in the machine. But that criticism
mistakes the problem. Newton exorcised the machine; he left
the ghost intact. The fact was understood by leading figures.
250 years ago David Hume recognized that "Newton seemed to
draw off the veil from some of the mysteries of nature," but "he
shewed at the same time the imperfections of the mechanical
philosophy; and thereby restored [Nature's] ultimate secrets
to that obscurity in which they ever did and ever will remain." The
world is simply not comprehensible to human intelligence,
at least in the ways that modern science had hoped and expected.
The classic scholarly study of the history of
materialism describes Newton's achievements as the destruction
of materialism or physicalism, in any serious sense of the
terms. It reviews how the expectations and goals of the pioneers
of the scientific revolution, and their materialist predecessors,
were abandoned, and we gradually "accustomed ourselves to
the abstract notion of forces, or rather to a notion hovering
in a mystic obscurity between abstraction and concrete comprehension," a "turning-point" in
the history of materialism that removes the doctrine far
from those of the "genuine Materialists" of the 17th century
and before, and deprives it of much significance.
These facts have considerable bearing on the study
of mind and brain today. In the light of Newton's demolition
of the concept of matter,
many scientists came to recognize that John Locke must have
been correct in suggesting that, just as the world has properties
of attraction and repulsion and others that "we can in no
way conceive motion bale to produce," so "a faculty of thinking" might
have been "superadded" to matter.
The term "matter" by then
had lost any significance, referring merely to the world,
with whatever strange properties it has, including Newtonian "absurdities" and
more extreme ones that had to be accepted as true in later
years.
By the end of the 18th century, Locke's
tentative suggestion was appropriately
rephrased by the famous chemist
Joseph Priestley as a virtual truism: "the powers
of sensation or perception and thought" are properties of "a
certain organized system of matter"; properties "termed mental" are
the result [of the] organical structure" of the brain and "the
human nervous system" generally.
Priestley of course had no idea how these properties
arise from the nervous system. Rather, much like the properties
of attraction, repulsion, chemical affinity, light, electricity
and magnetism, and others, mental properties had to be postulated
on the basis of experimental evidence, perhaps with the eventual
hope of unification, but without any prior idea of the form
that such unification might take.
Today, that traditional and virtually inevitable
conclusion has been revived, now formulated as a major thesis
that "Things mental, indeed minds, are emergent properties
of brains," though "we do not yet understand" the principles
that relate these emergent properties to those of cells.
The word "yet" again reflects the prevailing optimism. But
whatever speculations one may have about the prospects, the
thesis is not new; it is a traditional one, a direct consequence
of Newton's exorcism of the machine.
The history of chemistry provides revealing lessons
for the study of mental aspects of the world, and the course
it might take. Chemistry, of course, is hard science; right
next door to core physics in the rather misleading standard
hierarchy of "reducibility."
By the mid-18th century it was
understood that "chemical affinity must be accepted as a
first principle, which we cannot explain any more than Newton
could explain gravitation, and let us defer accounting for
the laws of affinity until we have established such a body
of doctrine as Newton has established concerning the laws
of gravitation" (English chemist Joseph Black).
That is pretty
much what happened. Chemistry proceeded
to establish a rich body of doctrine,"its triumphs . . . Built on no reductionist
foundation but rather achieved in isolation from the newly
emerging science of physics" (a leading contemporary historian
of chemistry, Arnold Thackrey). That continued until very
recently.
What was finally achieved 60 years ago, by Linus
Pauling, was not reduction: rather, unification, something
very different. A few years earlier, in 1929, Bertrand Russell,
who knew the sciences well, observed that chemical laws "cannot
at present be reduced to physical laws." But his phrase "cannot
at present" was shown to be wrong. It turned out that chemical
laws cannot in principle be reduced to physical laws, as
physical laws were understood.
Physics had to undergo fundamental
changes, mainly in the 1920s, in order
to be unified with basic chemistry. Physics had to "free itself" from "intuitive
pictures" and give up the hope of "visualizing the world," as
Heisenberg put it, another long leap away from intelligibility
in the sense of the scientific revolution of the 17th century.
As recently as 70 years ago, before the unification
was achieved, chemistry was regarded by many prominent scientists
as a calculating device, a way of organizing and predicting
the results of experiments, without any reality, because
it had not been reduced to core physics. The topic was hotly
debated, in terms that are very similar to those that dominate
much of contemporary thinking and debate in cognitive psychology
and philosophy of mind.
By the 1930s, it was understood that
the debate had been pointless, that
chemistry was real in the only sense of "reality" we have: it was the best theory
that could be constructed to understand chemical aspects
of the world. These quite recent developments in the core
natural sciences should, I think, be taken seriously in considering
higher mental faculties and the "bodies of doctrine" that
are being developed concerning them, language in particular.
The unification of biology and chemistry a few
years after Pauling's discovery can be misleading. That was
genuine reduction, but to a newly created physical chemistry;
some of the same people were involved, notably Pauling himself.
True reduction is not so common in the history of science,
and need not be assumed automatically to be a model for what
will happen in the future.
The study of human higher mental faculties might
well follow the course of the investigation of mechanical,
electromagnetic, optical, and chemical aspects of world,
among others. The hope for reduction may once again prove
illusory.
One cannot know, until we know, how unification
might take place - if it ever does -
and what form it will take; perhaps, once again, a radical
reconstruction of what is misleadingly called "the more basic" science. Perhaps
novel biochemical mechanisms and patterns of connectivity
are involved, as Mountcastle suggests. Or perhaps more radical
revisions, as often in the past.
In the last half century there has been intensive
and often highly productive inquiry into the brain, behavior,
and cognitive faculties of many organisms. The Holy Grail,
of course, is human higher mental faculties. But it should
be clear that this is the goal that is likely to be the most
remote, probably by orders of magnitude, if only because
of the complexity of the systems and their apparently novelty
and biological isolation.
Another serious barrier to inquiry is that direct
experimentation is excluded on ethical grounds - today, I
should add; not long ago practices were quite different,
in ways that we would now find extremely shocking. A lot
is known about the human visual system, but that is because
it is assumed to be rather like those of other mammals, including
other primates.
And for these animals, we permit ourselves
invasive experimentation, raising animals
in controlled environments, and so on. From such experimentation,
a great deal is learned, and the basic conclusions are reasonably
to hold for the human visual system as well.
But we know of no analogues
to language and other human mental organs,
we would presumably bar direct experimentation as we do for
humans. There is hope that new non-invasive technologies
- brain-imaging techniques and others - may offer a way around
this barrier to understanding. The prospects are exciting,
and a lot has already been learned.
But despite much important
progress in many areas, and justified
excitement about the prospects opened by newer technologies,
I think it is wise to be cautious in assessing what we know
and what we might realistically hope to learn.
For the present, the study of language and other
higher human mental faculties is proceeding much as chemistry
did, seeking to "establish a rich body of doctrine," and
sometimes succeeding, with an eye to eventual unification,
but without any clear idea of how this might take place.
Some of these bodies of doctrine are rather surprising in
their implications.
Thus in the case of language, very recent
work, some of the most important of
it conducted here, is providing interesting grounds for taking
seriously an idea that a few years ago would have seemed
outlandish: that the language organ of the brain approaches
a kind of optimal design, that it is in some interesting
sense an optimal solution to the minimum design specifications
the language organ must meet to be usable at all.
That is not what one expects to find in a highly
complex biological organ. At the very simplest level, say
cell division, or the structure of viruses, conclusions of
this sort seem very reasonable, and even partially understood.
But it has been commonly assumed that evolution
is a "tinkerer," in
the phrase of Nobel Laureate Francois Jacob, doing the best
it can with the materials at hand, the best typically being
human existence in fact does approach optimal design, that
would suggest that in some unknown way, it may be the result
of the functioning of physical and chemical laws for a brain
that has reached a certain level of complexity. And further
questions arise for general evolution that are by no means
novel, but that have been somewhat at the margins of inquiry
until fairly recently.
I'm thinking of the work of D'Arcy
Thompson and Alan Turing, to mention
two of the most prominent figures.
Perhaps I might add one final remark about the
limits of understanding. Many of the questions that inspired
the modern scientific revolution are not even on the agenda.
These include issues of will and choice, which were taken
to be the core of the mind-body problem - the problem that
was undermined by Newton, when he showed that there were
no bodies in any meaningful sense.
There has been very valuable
work about how an organism executes
a plan for some integrated motor action - how a cockroach
walks, or a person reaches for a cup on the table. But no
one even raises the question of why this plan is executed
rather than some other one, apart form the very simplest
organisms. Much the same is true even for visual perception,
sometimes considered to be a passive or reflexive operation.
Recently two MIT cognitive
neuroscientists published a review of
progress in solving a problem posed in 1850 by Helmholtz: "Even without moving
our eyes, we can focus our attention on different objects
at will, resulting in very different perceptual experiences
of the same visual field."
The phrase "at will" points to
an area beyond serious empirical inquiry. It remains as much
of a mystery as it was for Newton at the end of his life,
when he was still seeking some "subtle spirit" that lies
hidden in all bodies and that might, without "absurdity," account
for their properties of attraction and repulsion, the nature
and effects of light, sensation, and the way "member of animal
bodies move at the command of the will" - all comparable
mysteries for Newton. In the 17th century, the
ordinary use of language was taken
to be the prime illustration of this mystery, and the best
proof of the existence of other
minds. And for reasons we should not lightly dismiss.
For some of these mysteries, extraordinary bodies
of doctrine have been developed in the past several hundred
years, some of the greatest achievements of the human intellect.
And there have been remarkable feats of unification as well.
How remote the remaining mountain peaks may be, and even
just where they are, we can only guess.
Within the range
of feasible inquiry, there is plenty
of work to be done in understanding mental aspects of the
world, including human language. And the prospects are surely
exciting. We would do well, however, to keep in some corner
of our minds David Humes' conclusion about "Nature's ultimate secrets" and the "obscurity
in which they ever did and ever will remain and particularly
the reasoning that led him to that judgement, and its confirmation
in the subsequent history of the hard sciences.
These are
matters that are sometimes too
easily forgotten, I suspect, and that merit serious reflection
- possibly, some day, even constructive scientific inquiry.
Thank you.
