I have been asked
to comment on whether the universe shows signs of having been designed.1
I don't see how it's possible to talk about this without having at least some
vague idea of what a designer would be like. Any possible universe could be
explained as the work of some sort of designer. Even a universe that is
completely chaotic, without any laws or regularities at all, could be supposed
to have been designed by an idiot.
The question that seems to me to be worth answering, and perhaps not impossible
to answer, is whether the universe shows signs of having been designed by a
deity more or less like those of traditional monotheistic religions—not
necessarily a figure from the ceiling of the Sistine Chapel, but at least some
sort of personality, some intelligence, who created the universe and has some
special concern with life, in particular with human life. I expect that this is
not the idea of a designer held by many here. You may tell me that you are
thinking of something much more abstract, some cosmic spirit of order and
harmony, as Einstein did. You are certainly free to think that way, but then I
don't know why you use words like "designer" or "God,"
except perhaps as a form of protective coloration.
It used to be obvious that the world was designed by some sort of intelligence.
What else could account for fire and rain and lightning and earthquakes? Above
all, the wonderful abilities of living things seemed to point to a creator who
had a special interest in life. Today we understand most of these things in
terms of physical forces acting under impersonal laws. We don't yet know the
most fundamental laws, and we can't work out all the consequences of the laws we
do know. The human mind remains extraordinarily difficult to understand, but so
is the weather. We can't predict whether it will rain one month from today, but
we do know the rules that govern the rain, even though we can't always calculate
their consequences. I see nothing about the human mind any more than about the
weather that stands out as beyond the hope of understanding as a consequence of
impersonal laws acting over billions of years.
There do not seem to be any exceptions to this natural order, any miracles. I
have the impression that these days most theologians are embarrassed by talk of
miracles, but the great monotheistic faiths are founded on miracle stories—the
burning bush, the empty tomb, an angel dictating the Koran to Mohammed—and
some of these faiths teach that miracles continue at the present day. The
evidence for all these miracles seems to me to be considerably weaker than the
evidence for cold fusion, and I don't believe in cold fusion. Above all, today
we understand that even human beings are the result of natural selection acting
over millions of years of breeding and eating.
I'd guess that if we were to see the hand of the designer anywhere, it would be
in the fundamental principles, the final laws of nature, the book of rules that
govern all natural phenomena. We don't know the final laws yet, but as far as we
have been able to see, they are utterly impersonal and quite without any special
role for life. There is no life force. As Richard Feynman has said, when you
look at the universe and understand its laws, "the theory that it is all
arranged as a stage for God to watch man's struggle for good and evil seems
inadequate."
True, when quantum mechanics was new, some physicists thought that it put humans
back into the picture, because the principles of quantum mechanics tell us how
to calculate the probabilities of various results that might be found by a human
observer. But, starting with the work of Hugh Everett forty years ago, the
tendency of physicists who think deeply about these things has been to
reformulate quantum mechanics in an entirely objective way, with observers
treated just like everything else. I don't know if this program has been
completely successful yet, but I think it will be.
I have to admit that, even when physicists will have gone as far as they can go,
when we have a final theory, we will not have a completely satisfying picture of
the world, because we will still be left with the question "why?" Why
this theory, rather than some other theory? For example, why is the world
described by quantum mechanics? Quantum mechanics is the one part of our present
physics that is likely to survive intact in any future theory, but there is
nothing logically inevitable about quantum mechanics; I can imagine a universe
governed by Newtonian mechanics instead. So there seems to be an irreducible
mystery that science will not eliminate.
But religious theories of design have the same problem. Either you mean
something definite by a God, a designer, or you don't. If you don't, then what
are we talking about? If you do mean something definite by "God" or
"design," if for instance you believe in a God who is jealous, or
loving, or intelligent, or whimsical, then you still must confront the question
"why?" A religion may assert that the universe is governed by that
sort of God, rather than some other sort of God, and it may offer evidence for
this belief, but it cannot explain why this should be so.
In this respect, it seems to me that physics is in a better position to give us
a partly satisfying explanation of the world than religion can ever be, because
although physicists won't be able to explain why the laws of nature are what
they are and not something completely different, at least we may be able to
explain why they are not slightly different. For instance, no one has been able
to think of a logically consistent alternative to quantum mechanics that is only
slightly different. Once you start trying to make small changes in quantum
mechanics, you get into theories with negative probabilities or other logical
absurdities. When you combine quantum mechanics with relativity you increase its
logical fragility. You find that unless you arrange the theory in just the right
way you get nonsense, like effects preceding causes, or infinite probabilities.
Religious theories, on the other hand, seem to be infinitely flexible, with
nothing to prevent the invention of deities of any conceivable sort.
Now, it doesn't settle the matter for me to say that we cannot see the hand of a
designer in what we know about the fundamental principles of science. It might
be that, although these principles do not refer explicitly to life, much less
human life, they are nevertheless craftily designed to bring it about.
Some physicists have argued that certain constants of nature have values that
seem to have been mysteriously fine-tuned to just the values that allow for the
possibility of life, in a way that could only be explained by the intervention
of a designer with some special concern for life. I am not impressed with these
supposed instances of fine-tuning. For instance, one of the most frequently
quoted examples of fine-tuning has to do with a property of the nucleus of the
carbon atom. The matter left over from the first few minutes of the universe was
almost entirely hydrogen and helium, with virtually none of the heavier elements
like carbon, nitrogen, and oxygen that seem to be necessary for life. The heavy
elements that we find on earth were built up hundreds of millions of years later
in a first generation of stars, and then spewed out into the interstellar gas
out of which our solar system eventually formed.
The first step in the sequence of nuclear reactions that created the heavy
elements in early stars is usually the formation of a carbon nucleus out of
three helium nuclei. There is a negligible chance of producing a carbon nucleus
in its normal state (the state of lowest energy) in collisions of three helium
nuclei, but it would be possible to produce appreciable amounts of carbon in
stars if the carbon nucleus could exist in a radioactive state with an energy
roughly 7 million electron volts (MeV) above the energy of the normal state,
matching the energy of three helium nuclei, but (for reasons I'll come to
presently) not more than 7.7 MeV above the normal state.
This radioactive state of a carbon nucleus could be easily formed in stars from
three helium nuclei. After that, there would be no problem in producing ordinary
carbon; the carbon nucleus in its radioactive state would spontaneously emit
light and turn into carbon in its normal nonradioactive state, the state found
on earth. The critical point in producing carbon is the existence of a
radioactive state that can be produced in collisions of three helium nuclei.
In fact, the carbon nucleus is known experimentally to have just such a
radioactive state, with an energy 7.65 MeV above the normal state. At first
sight this may seem like a pretty close call; the energy of this radioactive
state of carbon misses being too high to allow the formation of carbon (and
hence of us) by only 0.05 MeV, which is less than one percent of 7.65 MeV. It
may appear that the constants of nature on which the properties of all nuclei
depend have been carefully fine-tuned to make life possible.
Looked at more closely, the fine-tuning of the constants of nature here does not
seem so fine. We have to consider the reason why the formation of carbon in
stars requires the existence of a radioactive state of carbon with an energy not
more than 7.7 MeV above the energy of the normal state. The reason is that the
carbon nuclei in this state are actually formed in a two-step process: first,
two helium nuclei combine to form the unstable nucleus of a beryllium isotope,
beryllium 8, which occasionally, before it falls apart, captures another helium
nucleus, forming a carbon nucleus in its radioactive state, which then decays
into normal carbon. The total energy of the beryllium 8 nucleus and a helium
nucleus at rest is 7.4 MeV above the energy of the normal state of the carbon
nucleus; so if the energy of the radioactive state of carbon were more than 7.7
MeV it could only be formed in a collision of a helium nucleus and a beryllium 8
nucleus if the energy of motion of these two nuclei were at least 0.3 MeV—an
energy which is extremely unlikely at the temperatures found in stars.
Thus the crucial thing that affects the production of carbon
in stars is not the 7.65 MeV energy of the radioactive state of carbon above its
normal state, but the 0.25 MeV energy of the radioactive state, an unstable
composite of a beryllium 8 nucleus and a helium nucleus, above the energy of
those nuclei at rest.2 This energy misses being too
high for the production of carbon by a fractional amount of 0.05 MeV/0.25 MeV,
or 20 percent, which is not such a close call after all.
This conclusion about the lessons to be learned from carbon synthesis is
somewhat controversial. In any case, there is one constant whose value does seem
remarkably well adjusted in our favor. It is the energy density of empty space,
also known as the cosmological constant. It could have any value, but from first
principles one would guess that this constant should be very large, and could be
positive or negative. If large and positive, the cosmological constant would act
as a repulsive force that increases with distance, a force that would prevent
matter from clumping together in the early universe, the process that was the
first step in forming galaxies and stars and planets and people. If large and
negative the cosmological constant would act as an attractive force increasing
with distance, a force that would almost immediately reverse the expansion of
the universe and cause it to recollapse, leaving no time for the evolution of
life. In fact, astronomical observations show that the cosmological constant is
quite small, very much smaller than would have been guessed from first
principles.
It is still too early to tell whether there is some fundamental principle that
can explain why the cosmological constant must be this small. But even if there
is no such principle, recent developments in cosmology offer the possibility of
an explanation of why the measured values of the cosmological constant and other
physical constants are favorable for the appearance of intelligent life.
According to the "chaotic inflation" theories of André Linde and
others, the expanding cloud of billions of galaxies that we call the big bang
may be just one fragment of a much larger universe in which big bangs go off all
the time, each one with different values for the fundamental constants.
In any such picture, in which the universe contains many parts with different
values for what we call the constants of nature, there would be no difficulty in
understanding why these constants take values favorable to intelligent life.
There would be a vast number of big bangs in which the constants of nature take
values unfavorable for life, and many fewer where life is possible. You
don't have to invoke a benevolent designer to explain why we are in one of the
parts of the universe where life is possible: in all the other parts of the
universe there is no one to raise the question.3 If
any theory of this general type turns out to be correct, then to conclude that
the constants of nature have been fine-tuned by a benevolent designer would be
like saying, "Isn't it wonderful that God put us here on earth, where
there's water and air and the surface gravity and temperature are so
comfortable, rather than some horrid place, like Mercury or Pluto?" Where
else in the solar system other than on earth could we have evolved?
Reasoning like this is called "anthropic." Sometimes it just amounts
to an assertion that the laws of nature are what they are so that we can exist,
without further explanation. This seems to me to be little more than mystical
mumbo jumbo. On the other hand, if there really is a large number of worlds in
which some constants take different values, then the anthropic explanation of
why in our world they take values favorable for life is just common sense, like
explaining why we live on the earth rather than Mercury or Pluto. The actual
value of the cosmological constant, recently measured by observations of the
motion of distant supernovas, is about what you would expect from this sort of
argument: it is just about small enough so that it does not interfere much with
the formation of galaxies. But we don't yet know enough about physics to tell
whether there are different parts of the universe in which what are usually
called the constants of physics really do take different values. This is not a
hopeless question; we will be able to answer it when we know more about the
quantum theory of gravitation than we do now.
It would be evidence for a benevolent designer if life were better than could be
expected on other grounds. To judge this, we should keep in mind that a certain
capacity for pleasure would readily have evolved through natural selection, as
an incentive to animals who need to eat and breed in order to pass on their
genes. It may not be likely that natural selection on any one planet would
produce animals who are fortunate enough to have the leisure and the ability to
do science and think abstractly, but our sample of what is produced by evolution
is very biased, by the fact that it is only in these fortunate cases that there
is anyone thinking about cosmic design. Astronomers call this a selection
effect.
The universe is very large, and perhaps infinite, so it should be no surprise
that, among the enormous number of planets that may support only unintelligent
life and the still vaster number that cannot support life at all, there is some
tiny fraction on which there are living beings who are capable of thinking about
the universe, as we are doing here. A journalist who has been assigned to
interview lottery winners may come to feel that some special providence has been
at work on their behalf, but he should keep in mind the much larger number of
lottery players whom he is not interviewing because they haven't won anything.
Thus, to judge whether our lives show evidence for a benevolent designer, we
have not only to ask whether life is better than would be expected in any case
from what we know about natural selection, but we need also to take into account
the bias introduced by the fact that it is we who are thinking about the
problem.
This is a question that you all will have to answer for yourselves. Being a
physicist is no help with questions like this, so I have to speak from my own
experience. My life has been remarkably happy, perhaps in the upper 99.99
percentile of human happiness, but even so, I have seen a mother die painfully
of cancer, a father's personality destroyed by Alzheimer's disease, and scores
of second and third cousins murdered in the Holocaust. Signs of a benevolent
designer are pretty well hidden.
The prevalence of evil and misery has always bothered those who believe in a
benevolent and omnipotent God. Sometimes God is excused by pointing to the need
for free will. Milton gives God this argument in Paradise Lost:
I formed them free, and free they must remain
Till they enthral themselves: I else must change
Their nature, and revoke the high decree
Unchangeable, eternal, which ordained
Their freedom; they themselves ordained their fall.
It seems a bit unfair to my relatives to be murdered in order to provide an
opportunity for free will for Germans, but even putting that aside, how does
free will account for cancer? Is it an opportunity of free will for tumors?
I don't need to argue here that the evil in the world proves that the universe
is not designed, but only that there are no signs of benevolence that might have
shown the hand of a designer. But in fact the perception that God cannot be
benevolent is very old. Plays by Aeschylus and Euripides make a quite explicit
statement that the gods are selfish and cruel, though they expect better
behavior from humans. God in the Old Testament tells us to bash the heads of
infidels and demands of us that we be willing to sacrifice our children's lives
at His orders, and the God of traditional Christianity and Islam damns us for
eternity if we do not worship him in the right manner. Is this a nice way to
behave? I know, I know, we are not supposed to judge God according to human
standards, but you see the problem here: If we are not yet convinced of His
existence, and are looking for signs of His benevolence, then what other
standards can we use?
The issues that I have been asked to address here will seem to many to be
terribly old-fashioned. The "argument from design" made by the English
theologian William Paley is not on most peoples' minds these days. The prestige
of religion seems today to derive from what people take to be its moral
influence, rather than from what they may think has been its success in
accounting for what we see in nature. Conversely, I have to admit that, although
I really don't believe in a cosmic designer, the reason that I am taking the
trouble to argue about it is that I think that on balance the moral influence of
religion has been awful.
This is much too big a question to be settled here. On one side, I could point
out endless examples of the harm done by religious enthusiasm, through a long
history of pogroms, crusades, and jihads. In our own century it was a Muslim
zealot who killed Sadat, a Jewish zealot who killed Rabin, and a Hindu zealot
who killed Gandhi. No one would say that Hitler was a Christian zealot, but it
is hard to imagine Nazism taking the form it did without the foundation provided
by centuries of Christian anti-Semitism. On the other side, many admirers of
religion would set countless examples of the good done by religion. For
instance, in his recent book Imagined Worlds, the distinguished physicist
Freeman Dyson has emphasized the role of religious belief in the suppression of
slavery. I'd like to comment briefly on this point, not to try to prove anything
with one example but just to illustrate what I think about the moral influence
of religion.
It is certainly true that the campaign against slavery and the slave trade was
greatly strengthened by devout Christians, including the Evangelical layman
William Wilberforce in England and the Unitarian minister William Ellery
Channing in America. But Christianity, like other great world religions, lived
comfortably with slavery for many centuries, and slavery was endorsed in the New
Testament. So what was different for anti-slavery Christians like Wilberforce
and Channing? There had been no discovery of new sacred scriptures, and neither
Wilberforce nor Channing claimed to have received any supernatural revelations.
Rather, the eighteenth century had seen a widespread increase in rationality and
humanitarianism that led others—for instance, Adam Smith, Jeremy Bentham, and
Richard Brinsley Sheridan—also to oppose slavery, on grounds having nothing to
do with religion. Lord Mansfield, the author of the decision in Somersett's
Case, which ended slavery in England (though not its colonies), was no more than
conventionally religious, and his decision did not mention religious arguments.
Although Wilberforce was the instigator of the campaign against the slave trade
in the 1790s, this movement had essential support from many in Parliament like
Fox and Pitt, who were not known for their piety. As far as I can tell, the
moral tone of religion benefited more from the spirit of the times than the
spirit of the times benefited from religion.
Where religion did make a difference, it was more in support of slavery than in
opposition to it. Arguments from scripture were used in Parliament to defend the
slave trade. Frederick Douglass told in his Narrative how his condition as a
slave became worse when his master underwent a religious conversion that allowed
him to justify slavery as the punishment of the children of Ham. Mark Twain
described his mother as a genuinely good person, whose soft heart pitied even
Satan, but who had no doubt about the legitimacy of slavery, because in years of
living in antebellum Missouri she had never heard any sermon opposing slavery,
but only countless sermons preaching that slavery was God's will. With or
without religion, good people can behave well and bad people can do evil; but
for good people to do evil—that takes religion.
In an e-mail message from the American Association for the Advancement of
Science I learned that the aim of this conference is to have a constructive
dialogue between science and religion. I am all in favor of a dialogue between
science and religion, but not a constructive dialogue. One of the great
achievements of science has been, if not to make it impossible for intelligent
people to be religious, then at least to make it possible for them not to be
religious. We should not retreat from this accomplishment.
1 This article is
based on a talk given in April 1999 at the Conference on Cosmic Design of the
American Association for the Advancement of Science in Washington, D.C. back
2 This was pointed out in a 1989 paper by M. Livio, D.
Hollowell, A. Weiss, and J.W. Truran ("The anthropic significance of the
existence of an excited state of 12C," Nature, Vol. 340, No. 6231, July 27,
1989). They did the calculation quoted here of the 7.7 MeV maximum energy of the
radioactive state of carbon, above which little carbon is formed in stars. back
3 The same conclusion may be reached in a more subtle way
when quantum mechanics is applied to the whole universe. Through a
reinterpretation of earlier work by Stephen Hawking, Sidney Coleman has shown
how quantum mechanical effects can lead to a split of the history of the
universe (more precisely, in what is called the wave function of the universe)
into a huge number of separate possibilities, each one corresponding to a
different set of fundamental constants. See Sidney Coleman, "Black Holes as
Red Herrings: Topological fluctuations and the loss of quantum coherence,"
Nuclear Physics, Vol. B307 (1988), p. 867. back