Van Huyssteen J.W. (editor) Encyclopedia of Science and Religion

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GOD,EXISTENCE OF

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Bibliography

Hofstadter, Douglas R. “Analogies and Metaphors to Ex-

plain Gödel’s Theorem.” In Mathematics: People,

Problems, Results, eds. Douglas M. Campbell and

John C. Higgins. Belmont, Calif.: Wadsworth Interna-

tional, 1984.

Nagel, Ernest, and Newman, James R. Gödel’s Proof. New

York: New York University Press, 1958.

W. M. PRIESTLEY

GOD,EXISTENCE OF

Most theists tend to think of God as the Supreme

Being. Human knowledge and power are strictly

limited, while God is omniscient and omnipotent.

But humans are beings and God is a vastly supe-

rior being. Hence human beings exist and God ex-

ists in exactly the same sense. The tradition of

Christian theology, however, also contains concep-

tions of the differences separating God and crea-

tures that are more radical. According to Thomas

Aquinas (c. 1225–1274), for example, there is in

human beings a distinction between essence,

which is to say what human beings are, and exis-

tence. But in God essence and existence are iden-

tical; God’s essence is to exist. God is Being Itself,

not one being among others. Thus humans exist

and God exists in different though analogously re-

lated senses. And an even more radical separation

is found in the mystical theology of Meister Eckhart

(1260–1328). He distinguishes between God (Gott)

and the Godhead (Gottheit). The Godhead is an as-

pect or dimension of divine reality that is above or

beyond being. It is neither a being nor Being Itself.

Paradoxically, it cannot be said to exist, even

though it is the Ultimate Reality. Jean-Luc Marion

develops a conception of this sort in his aptly titled

God Without Being (1991).

Evidential support for claims about the exis-

tence of God comes from several sources. They in-

clude religious experience, revelation, and theo-

logical reflection. According to William P. Alston’s

Perceiving God (1991), claims about how God is

interacting with a human subject of religious expe-

rience derive prima facie epistemic justification

from a kind of nonsensory perception in which it

seems to the subject that God is performing actions

of various sorts. The God encountered in such ex-

periences is taken to be a being capable of inter-

acting with human beings. In the Hebrew Bible,

when Moses asks God to make known the divine

name, God says in response to Moses, “I am who

I am” (Exod. 3:14). According to some interpreta-

tions, it is revealed by means of this response that

God is Being Itself. The idea that God is not just a

being among beings thus derives epistemic war-

rant from scriptural revelation. And in The Courage

to Be (1952), Paul Tillich speaks of the God above

the God of theism. He also claims that the divine

Ultimate Reality is not a being or even Being Itself,

but is instead the Ground of Being. Theological re-

flection therefore lends credibility to the claim that

God is somehow beyond being.

However, one must turn to certain parts of nat-

ural theology if one wishes to find a source of ev-

idence for the existence of God that is sensitive to

empirical science. According to Immanuel Kant

(1724–1804), natural theology’s main arguments for

God’s existence may be classified as ontological,

cosmological, or teleological. Anselm of Canter-

bury (c. 1033–1109) is the author of the first and

most famous ontological argument. He attempted

to derive the existence of God from the idea of

God as a being greater than which cannot be con-

ceived. But since the premises of ontological argu-

ments are supposed to be knowable a priori and

so independent of human experience of the world,

such arguments do not in any way rely on scien-

tific knowledge of that world.

Cosmological arguments do appeal to premises

about the empirical world that is the object of sci-

entific inquiry. Two familiar cosmological arguments

are among Aquinas’s celebrated five ways of prov-

ing the existence of God. One starts from the prem-

ise that there are now things undergoing change

and things causing change; it concludes that an un-

changing first cause of change exists. The other

starts from the premise that there are contingent

things that might not have existed; it concludes that

there is a necessary being on which contingent

things depend for their existence. Because the

premises of these two arguments invoke only very

general features of the world that humans experi-

ence, their truth does not depend on the details of

the scientific worldview. There are, however, cos-

mological arguments that are sensitive to such de-

tails. In his contribution to Theism, Atheism, and Big

Bang Cosmology (1993), William Lane Craig argues

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for God’s existence from physical cosmology. Ac-

cording to Big Bang cosmology, the cosmos began

to exist twelve to fifteen billion years ago. Reason-

ing from the principle that anything that begins to

exist must be brought into existence by something,

Craig concludes that God brought the cosmos into

existence. Craig’s argument is, of course, quite con-

troversial. In his contribution to Theism, Atheism,

and Big Bang Cosmology, Quentin Smith contends

that Big Bang cosmology provides the basis for a

successful argument to atheism.

But science bears most directly on natural the-

ology through teleological or design arguments. The

best known design argument is contained in

William Paley’s Natural Theology (1802). Paley ar-

gues for an analogy between the order displayed by

biological structures, such as the human eye, and

the order of mechanical devices, such as watches

that are known to be products of design, and he

concludes that God designed those biological struc-

tures. This sort of analogical design argument was

subjected to devastating criticism by David Hume

(1711–1776), and Darwinian mechanisms involving

variation and natural selection have successfully ex-

plained a great deal of biological order. So Paley’s

design argument has lost its popularity.

More recent design arguments appeal to other

sorts of natural order. In The Existence of God

(1979), Richard Swinburne argues that the temporal

order in the cosmos expressed by natural laws to-

gether with the fact that nature is composed of only

a few elementary building blocks are evidence of

design. He concludes that this evidence boosts the

probability of God’s existence. Others have drawn

attention to the fact that various parameters such as

certain physical constants and initial conditions of

the cosmos at the Big Bang must lie within nar-

rowly restricted limits if life is to evolve. They con-

tend that God fine-tuned those parameters for the

purpose of producing either life of some sort or

other, or human life in particular. These arguments

too have turned out to be controversial.

And in the United States, the Intelligent Design

creationism movement aims to overthrow Darwin-

ism. Michael Behe, one of the prominent figures in

this movement, argues in Darwin’s Black Box

(1996) that molecular and cell biology have re-

vealed irreducible biological complexity that can-

not be explained in terms of Darwinian mecha-

nisms of variation and natural selection. Behe’s

view is that such complexity is the product of di-

vine design. Intelligent Design creationism has

been vigorously disputed by many scientists and

philosophers. A balanced and comprehensive

presentation of the views on both sides of this new

outbreak of warfare between science and religion

may be found in Intelligent Design Creationism

and Its Critics (2001), a volume edited by Robert T.

Pennock. It remains an open question whether any

part of scientific knowledge supports or under-

mines belief in the existence of God.

See also COSMOLOGICAL ARGUMENT;DESIGN;INTELLIGENT

DESIGN;ONTOLOGICAL ARGUMENT;TELEOLOGICAL

ARGUMENT

Bibliography

Alston, William P. Perceiving God: The Epistemology of Re-

ligious Experience. Ithaca, N.Y.: Cornell University

Press, 1991.

Behe, Michael. Darwin’s Black Box: The Biochemical

Challenge to Evolution. New York: Free Press, 1996.

Craig, William Lane, and Smith, Quentin. Theism, Atheism,

and Big Bang Cosmology. New York and Oxford: Ox-

ford University Press, 1993.

Marion, Jean-Luc. God Without Being, trans. Thomas A.

Carlson. Chicago: University of Chicago Press, 1991.

Paley, William. Natural Theology. London: Faulder;

Philadelphia, Pa.: John Morgan, 1802.

Pennock, Robert T., ed. Intelligent Design Creationism

and Its Critics. Cambridge, Mass.: MIT Press, 2001.

Swinburne, Richard. The Existence of God. Oxford: Claren-

don Press, 1979.

Tillich, Paul. The Courage to Be. New Haven, Conn.: Yale

University Press, 1952.

PHILIP L. QUINN

GOD OF THE GAPS

The phrase God of the gaps refers to attempts to

use statements about divine intervention in the

physical world to fill in the “gaps” in scientific ex-

planation. It is the attempt to introduce God as an

explanatory hypothesis on the level of efficient

causality to make up for limitations in current sci-

entific understanding. The approach simply does

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not work because eventually scientific understand-

ing closes the gap, making the appeal to divine ex-

planation irrelevant. The approach is not taken se-

riously as a way of relating science and religion

because it violates several fundamental principles

of causal analysis and explanation in both science

and theology.

History

The phrase God of the gaps is often credited to

Charles A. Coulson in his book Science and Chris-

tian Belief (1955). This is certainly one of the first

places where the phrase appears in material di-

rectly related to the science and religion discus-

sion, but there are antecedents that appear years or

even centuries earlier. In his Letters and Papers

from Prison, German theologian Dietrich Bonhoef-

fer in correspondence from May 25, 1944, observes

in response to Carl F. von Weizsacker’s The World-

view of Physics that:

Weizsacker’s book . . . brought home to

me how wrong it is to use God as a stop-

gap for the incompleteness of our knowl-

edge. For the frontiers of knowledge are

inevitably being pushed back further and

further, which means that you only think

of God as a stop-gap. He also is being

pushed back further and further, and is in

more or less continuous retreat. We should

find God in what we do know, not in what

we don’t . . . (p. 190–191).

Bonhoeffer clearly saw the danger of placing

God on the level of secondary causal explanation.

God and the God hypothesis would be edged out,

just as the astronomer Marquis de Laplace replied

“I had no need of that hypothesis” when Napoleon

asked why he did not discuss God in his writings.

According to Ian Barbour in Religion and Science:

Historical and Contemporary Issues (1997):

The “God of the gaps” was as unnecessary

in biology after Darwin as it had been in

physics after Laplace. Adaptive changes

could be accounted for by random varia-

tion and natural selection without involv-

ing divine intervention. We have Darwin

to thank for finally making it clear that God

is neither a secondary cause operating on

the same level as natural forces nor a

means for filling gaps in the scientific ac-

count. (p. 73)

The concept of God intervening from beyond

to fill in inadequate knowledge or to resolve

human problems actually goes back in Western

culture to the ancient Greeks and the understand-

ing of a deus ex machina (god of the machine)

found in Greek theater. When a plot became too

convoluted (or the audience’s patience and en-

durance was wearing thin) an actor wearing the

mask of the appropriate Greek deity would literally

be lowered onto the stage from above by a crane

(the machine) and resolve the plot conflicts, re-

store order, and serve out justice. In later thought,

the phrase deus ex machina came to refer to any

theological concept that involved God directing

human or earthly events by dropping out of the su-

pernatural into the natural. The ad hoc character of

the concept expresses a form of theological des-

peration in which divine involvement cannot be

understood in a coherent way with other forms of

rational explanation.

Analysis

Since the time of Aristotle in Western culture a dis-

tinction has been made between primary and sec-

ondary causal analysis. Primary causal analysis

(formal and final) has to do with the ends or pur-

poses of any physical existent and secondary

analysis with the means for its arisal (material and

efficient). The great gains in scientific analysis have

been accomplished at least in part by focusing on

secondary analysis, which is observable, measura-

ble, and repeatable. The power of scientific analy-

sis lies precisely in the intentional limiting of the

questions to the physically empirical and verifiable.

Science as part of its methodology assumes that

there will be material and efficient explanations of

physical phenomena, that is, the methodology is

inclusive of secondary causal analysis. This focus is

at the heart of the scientific revolution of the sev-

enteenth century. Theology and philosophy on the

other hand have focused on the origins and ends

of physical existence. To introduce God as a part

of the secondary causal analysis violates principles

of scientific understanding and commits a category

mistake in causal analysis.

It must also be said that a constructive rela-

tionship between religion and science would in-

volve connecting the two forms of causal analysis.

Multiple strategies have been proposed for this

with God working either “before” or “behind” the

physical systems. The former was approached in

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Enlightenment deism, where God arranged every-

thing “before” the creation like a divine clock-

maker and then left the created order to run on its

own. This position, while popular in the eigh-

teenth century, was later seen to deny the under-

standing of God involved in a continuing creation

(creatio continua) and to be contradictory to the

Abrahamic faith traditions.

Since about 1990 attention has been devoted

to formulating theories where God works in and

through the physical systems, such as in quantum

indeterminacy, without violating known physical

or biological laws. This “causal joint” discussion

has resulted in a number of new theories of divine

action ranging from top-down or whole-part causa-

tion (Arthur Peacocke) to bottom-up (Robert John

Russell), Persuasion ( John Cobb, David Griffin),

Information ( John Polkinghorne), or Self-

Limitation (W. H. Vanstone), to name a few. What

unites these diverse approaches is their commit-

ment to respect the various physical and life sci-

ences in their causal analyses and yet provide op-

portunities for dialogue on boundary questions,

the ethical application of scientific technology, and

other areas of common concern. Mutual respect

between science and religion permits this in a way

that a “God of the gaps” approach does not be-

cause it violates the integrity of both. For these

reasons, among others, both “God of the gaps”

and deus ex machina are not seen as viable con-

cepts for theological understanding in relating sci-

ence and religion.

See also ARISTOTLE; CAUSALITY, PRIMARY AND

SECONDARY; CAUSATION; CREATIO CONTINUA;

REATIO EX NIHILO; CREATION; DEISM; DIVINE

ACTION; GOD; GOD, EXISTENCE OF; SKYHOOKS

Bibliography

Barbour, Ian. Religion and Science: Historical and Con-

temporary Issues. San Francisco: Harper, 1997.

Berg, Christian. “Leaving Behind the God-of-the-Gaps: To-

ward a Theological Response to Limit Questions.” In

Expanding Humanity’s Vision of God, ed. Robert

Hermann. Philadelphia: Templeton Foundation Press.

2001.

Bonhoeffer, Dietrich. Letters and Papers From Prison, ed.

Eberhard Bethge. New York: Macmillan, 1953.

Coulson, Charles A. Science and Christian Belief. Chapel

Hill: University of North Carolina Press, 1955.

Southgate, Christopher, et al. God, Humanity, and the

Cosmos: A Textbook in Science and Religion. Harris-

burg, Pa.: Trinity Press, 1999.

ERNEST SIMMONS

GOULD,STEPHEN JAY

Stephen Jay Gould was born on September 10,

1941, in New York City. He was educated at Anti-

och College in Ohio and then trained as a paleon-

tologist, doing his doctoral work at Columbia Uni-

versity in New York. His first academic position

was at Harvard University in Cambridge, Massa-

chusetts, where he remained for the rest of his life,

later adding to his responsibilities a curatorship in

paleontology at the American Museum of Natural

History in New York. Gould received many hon-

ors, including numerous honorary doctoral de-

grees, and was a member of the National Academy

of Sciences.

Gould’s early scientific work focused on land

snails in Bermuda, and at first he worked in a fairly

conventional Darwinian fashion, seeing natural se-

lection as the main cause of evolutionary change.

But soon, he and paleontologist Niles Eldredge

began trying to break the paradigm of conven-

tional Darwinism, which sees the fossil record as

essentially flowing from one form to another, with

all gaps due to inadequacies in the record. Gould

and Eldredge forwarded a theory of punctuated

equilibrium, arguing that the fossil record shows

stasis (no appreciable change, for periods of time,

in some particular line of organisms), followed by

very rapid change. The gaps in the record there-

fore reflect real gaps in the fossilization process.

Gould held to the theory of punctuated equi-

librium throughout his life, although the causal

mechanism for the process was often in flux and

not entirely clear. For a while, Gould floated the

idea of saltations (real macromutations that jump

from one species to another), but this theory was

criticized by population geneticists, causing Gould

to look for other non-Darwinian, nonselective

mechanisms. Together with molecular evolutionist

Richard Lewontin, Gould argued that many aspects

of organic nature are nonadaptive and could not

have been produced by selection. Lewontin and

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Gould argued that many features of plants and an-

imals are like spandrels (the tops of columns in

medieval churches); they are simply byproducts of

the building process and thus without any great bi-

ological significance.

Much of Gould’s work was not presented di-

rectly to his fellow professionals. He was a master

at writing for a general audience, especially in

essay form. For thirty years he wrote a monthly

column called “This View of Life” in the magazine

Natural History. In this column, Gould explored

hundreds of different topics, not all of them related

to biology. The essays were collected in several

very successful volumes, beginning with Ever Since

Darwin (1977). Gould also wrote books on general

topics, including the history of brain science in The

Mismeasure of Man (1981) and the fossils of the

Burgess Shale in Canada in Wonderful Life (1989).

At the scholarly level, Gould published numerous

articles on the nature of the fossil record, usually in

the journal Paleobiology, and the book Ontogeny

and Phylogeny (1977) on the importance of devel-

opment. Just before he died, Gould completed The

Structure of Evolutionary Theory (2002), a compre-

hensive book covering all of his thoughts about

evolution. In this last book, Gould turned to the

history of science, as he had often done earlier, not

merely to develop his ideas but to demonstrate that

he was part of a respectable tradition, while his op-

ponents were not.

Gould was admired by the general public, but

many of his fellow evolutionists were less open in

their praise, perhaps because of professional jeal-

ousy combined with discomfort at Gould’s arro-

gant nature. Some critics felt that Gould’s ideas

were, scientifically speaking, somewhat shallow:

Detailed examination did not always bear them

out. By the time of Gould’s death, consensus on

the Eldredge-Gould claim about the nature of the

fossil record was that it probably has merit, al-

though there are many exceptions. The lack of a

convincing causal hypothesis for punctuated equi-

librium certainly counts against it. However,

Gould’s early stress on the importance of develop-

ment for a full understanding of the evolutionary

process seems fully borne out as molecular biolo-

gists turn their interests to questions of history.

Gould admitted that he always wrote with a

concern for the morality beneath the surface of his

science. A nonpracticing Jew with a Marxist back-

ground (the lasting influence of which was a mat-

ter of debate), he felt strongly about all matters of

prejudice. In the 1970s, Gould was one of the lead-

ers against sociobiology’s attempts to explain

human nature in terms of biology. Gould argued

that sociobiology was not real science, but simply

conservative ideology in fancy dress. For him, cul-

ture is essentially a spandrel, with no real biologi-

cal importance. Undoubtedly the Lewontin-Gould

attack on adaptation was motivated in part by this

continued critique. Sociobiologists argued strongly

that human nature is directly adaptive, such that

men and women, for example, are psychologically

as well as physically different because of their biol-

ogy. Gould was determined to counter such views.

Gould also saw claims about biological

progress as being part and parcel of the offensive

ideology against which he fought, which set hu-

mans at the top of the animal hierarchy, with white

gentiles at the top of the human chain. Gould saw

Darwinism, with its emphasis on the success of the

fittest, as badly bound up with claims about

progress, and this was another reason to attack

adaptationism. Many of Gould’s popular works, es-

pecially The Mismeasure of Man and Wonderful

Life, were explicit critiques on progressionism.

Whether or not Gould was correct, such views

brought him into conflict with many of his fellow

evolutionists. British science writer Richard

Dawkins, an ardent Darwinian and progressionist,

took strong offence at Gould’s thinking, which

Dawkins felt distorted and belittled the opposition.

In one of his essays, Gould accused the Jesuit pa-

leontologist Pierre Teilhard de Chardin of being re-

sponsible for the Piltdown hoax. Many critics, par-

ticularly many Catholics, took umbrage at this

accusation, since Gould’s evidence was slim. Care-

ful examination of the essay, however, shows that

Gould’s real intent may have been to read Teilhard

out of science. As the twentieth century’s most ar-

dent progressionist, Teilhard had to be exposed as

a man without moral or scientific authority.

Despite this attack on Teilhard, Gould’s atti-

tude toward religion was far more complex than

that of a typical atheist. Although a nonbeliever,

Gould had a passion for singing oratorio, which

was equaled by his passion for baseball. He was,

in a sense, a deeply religious man, despite the ab-

sence of any formal theology. He knew the Bible,

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both the Old and New Testaments, very well, and

he frequently used biblical stories or allusions to il-

lustrate points in his science writing. As an ardent

evolutionist, Gould stood firmly against biblical lit-

eralists and creationists, and in 1981 he served as

an expert witness for the American Civil Liberties

Union in its successful litigation against a creation-

ist law that had been passed in Arkansas. One of

his last books, Rocks of Ages (1999), deals explicitly

with issues of science and religion. Gould takes the

position of the neo-orthodox (like Langdon

Gilkey), arguing that science and religion are dif-

ferent dimensions for understanding and feeling—

he calls them magisteria—and hence can not

come into conflict if properly understood.

Unfortunately, Gould never really explored the

ways in which conflict is avoided, and one is left

with the impression that any compromise is going

to favor religion. Gould’s worldview would not

allow miracles, for instance, and hence it would be

necessary to interpret the resurrection symbolically

or metaphorically. Such an approach may be ac-

ceptable to some Christians, but not to all, or in-

deed to most. In a way, therefore, Gould comes

across as a logical positivist who is prepared to

allow a role for religion as long as it is confined to

sentiment, feeling, and morality, but makes no

claims about matters of fact.

Gould died on May 20, 2002, in New York City.

It is difficult to make long-term predictions about

his lasting influence, although he will surely al-

ways be celebrated as a brilliant popular writer. It

is less likely that he will be remembered as a sig-

nificant scientist or as a major player in the debate

about science and religion.

See also ADAPTATION; CREATIONISM; DARWIN, CHARLES;

VOLUTION, BIOLOGICAL; POSITIVISM, LOGICAL;

OCIOBIOLOGY; TEILHARD DE CHARDIN, PIERRE

Bibliography

Eldredge, Niles, and Gould, Stephen Jay. “Punctuated

Equilibria: An Alternative to Phyletic Gradualism.” In

Models in Paleobiology, ed. Thomas. J. M. Schopf. San

Francisco: Freeman Cooper, 1972.

Gould, Stephen Jay. Ever Since Darwin: Reflections in

Natural History. New York: Norton, 1977.

Gould, Stephen Jay. Ontogeny and Phylogeny. Cambridge,

Mass.: Belknap, 1977.

Gould, Stephen Jay. “The Piltdown Conspiracy.” Natural

History 89 (1980): 8–28.

Gould, Stephen Jay. The Mismeasure of Man. New York:

Norton, 1981.

Gould, Stephen Jay. Wonderful Life: The Burgess Shale

and the Nature of History. New York: Norton, 1989.

Gould, Stephen Jay. Rocks of Ages: Science and Religion

in the Fullness of Life. New York: Norton, 1999.

Gould, Stephen Jay. The Structure of Evolutionary Theory.

Cambridge, Mass.: Harvard University Press, 2002.

Ruse, Michael. The Darwinian Paradigm: Essays on Its

History, Philosophy, and Religious Implications. Lon-

don: Routledge, 1989.

Ruse, Michael. Monad to Man: The Concept of Progress in

Evolutionary Biology. Cambridge, Mass.: Harvard Uni-

versity Press, 1996.

Ruse, Michael. Mystery of Mysteries: Is Evolution a Social

Construction? Cambridge, Mass.: Harvard University

Press, 1999.

Ruse, Michael. Darwin and Design: Science, Philosophy,

Religion. Cambridge, Mass.: Harvard University Press,

2003.

MICHAEL RUSE

GRADUALISM

Gradualism, also called phyletic gradualism, is the

view that the course of evolution is gradual with

small changes accumulating through time. Gradu-

alism is opposed to punctualism, where evolu-

tionary change is thought to happen in short

episodes of rapid evolution followed by long peri-

ods of stasis when little or no evolutionary change

occurs. The latter view is based on the interpreta-

tion of the fossil record and is common among

palaeontologists, whereas the former view builds

on a version of population genetics theory. How-

ever, most evolutionary biologists hold the view

that the two concepts are not necessarily contra-

dictory because gradual changes in genotype may

occasionally lead to major changes in phenotype.

See also CATASTROPHISM; EVOLUTION; PUNCTUATED

EQUILIBRIUM

VOLKER LOESCHCKE

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GRAND UNIFIED THEORY

A Grand Unified Theory (GUT) unifies, or interre-

lates in a single quantum field interaction, the three

fundamental nongravitational forces: electromag-

netism, the weak nuclear interaction, and the

strong nuclear interaction. These three forces are

each characterized by a coupling constant, which

gives the strength of the interaction by a range

over which the force acts (long-range like electro-

magnetism, or short-range like the two nuclear

forces), and by certain characteristic symmetries

that are described by mathematical symmetry

groups. A successful GUT would show how the

three different coupling constants become identical

at some very high energy, subsume the symmetries

of the three individual interactions in a much larger

symmetry group, and explain all of the masses,

processes, couplings, decays, ranges, and other be-

haviors of all particles at lower energies—lower

than the GUT unification energy. The current stan-

dard model of particle physics, though highly suc-

cessful in other ways, does not do this. Further,

there are strong indications that a more complete

and adequate explanation, describing deep con-

nections that have so far evaded our understand-

ing, awaits a successful GUT model.

A GUT would express the fact that at the most

fundamental level all nongravitational interactions,

and all particles, quarks, electrons, and neutrinos,

are intimately interrelated and, in fact, identical

above the unification energy. Their difference at

low energies is expressed in a GUT by saying that

the symmetries characterizing the interactions at

very high energies, rendering particles and forces

identical or equivalent, are “spontaneously broken”

below the unification energy. Such spontaneously

broken symmetries are present in the underlying

relationships characterizing the system, but are not

expressed—are hidden—in a given equilibrium

state of the system, such as that realized in the

present state of the universe. Construction of a

GUT theory is an essential step towards achieving

total unification, which would also include gravity.

Although promising and detailed progress has

been made on a number of fronts, there was no

adequate GUT as of 2002.

There are strong indications that all the basic

physical interactions are intimately related and that

they can be unified. In the mid nineteenth century,

the Scottish physicist James Clerk Maxwell began

realizing this intuition by unifying electrical and

magnetic phenomena in his electromagnetic the-

ory. In the 1970s, Sheldon Glashow, Stephen Wein-

berg, and Abdus Salam succeeded in developing an

adequate electroweak theory, which describes how

electromagnetism and the weak nuclear interaction

are related, and how they are identical at tempera-

tures above 10

K (kelvin). This electroweak the-

ory was confirmed in 1983 by the discovery of the

W and Z massive bosons, which carry the elec-

troweak force and which were predicted by the

theory. A completely successful GUT would incor-

porate the strong nuclear interaction with this elec-

troweak interaction in an analogous way at some

higher temperature above 10

Part of the motivation for a GUT is the lack of

explanation for many of the parameters and char-

acteristics of the standard model, and of the uni-

verse itself. For example, there is no explanation

for the baryon-anti-baryon asymmetry, which

means that there is more matter in the universe

than there is antimatter. There is also some positive

experimental support for a GUT, including equality

of the magnitude of the charges of the proton and

the electron and the non-zero rest-mass of the neu-

trino. Furthermore, GUT candidates generically

predict the decay of protons at some very slow

rate, as well as the presence of monopoles and

other topological defects, which are localized re-

gions in which the vacuum energy is different from

the rest of the universe (false vacuum). Observa-

tional limits on these phenomena are being used,

and will continue to be used, to identify the most

adequate GUT candidates.

From a cosmological point of view, the success

of a GUT would mean that at some very early stage

in the history of the universe—well before one sec-

ond after the Big Bang, when the temperature of

the universe was greater than 10

K—the physics

of the universe was characterized by just two in-

teractions: gravity and the GUT interaction. The

universe would have been much too hot for pro-

tons, neutrons, and electrons to exist, as they do at

lower temperatures. As the universe expanded, it

cooled. And, as it cooled below 10

K, the GUT

interaction split into the strong nuclear and the

electroweak interactions. A short time later—still

much less than one second after the Big Bang—

when the temperature had plummeted below 10

K, the electroweak interaction split further into the

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weak nuclear and the electromagnetic interactions.

From that point on, the basic physics of the uni-

verse was the same as it is today, but devoid of the

complex macroscopic and microscopic structures

that developed much later.

Implications for theology

There are no direct implications of GUT unification

for religion and theology, but there are several im-

portant indirect influences. First, GUT unification,

when it is finally achieved, will contribute to de-

scribing how everything in material reality is inti-

mately interconnected in very basic ways. Those

relationships constitute reality as it is and are an es-

sential part of how God’s continuing creative ac-

tion is realized—through these “laws of nature.”

Second, a GUT characterizes a definite, very early

stage in the evolution of the universe. A successful

GUT will strengthen the already strong case for the

evolution of the presently lumpy, cool, complex,

and highly differentiated cosmos from a very hot,

simple, homogeneous, and relatively undifferenti-

ated primordial state, which was characterized by a

much simpler physics. For the theistic thinker, a

GUT represents one of the key ways in which God

gradually brought into being the reality of which

human beings are a part.

See also FIELD THEORIES

Bibliography

Bailin, David, and Love, Alexander. “Grand Unified The-

ory.” In Introduction to Gauge Field Theory, rev.

edition. Bristol, UK, and Philadelphia: Institute of

Physics, 1993.

Börner, Gerhard. “Grand Unification Schemes.” In The

Early Universe: Facts and Fiction, 3rd edition. Berlin,

Heidelberg, and New York: Springer-Verlag, 1993.

Collins, P. D. B.; Martin, A. D.; and Squires, E. J. “Grand

Unified Theories.” In Particle Physics and Cosmology.

New York: Wiley, 1989.

Davies, Paul. “The New Physics: A Synthesis.” In The New

Physics, ed. Paul Davies. Cambridge, UK: Cambridge

University Press, 1989.

Georgi, Howard. “Grand Unified Theories.” In The New

Physics, ed. Paul Davies. Cambridge, UK: Cambridge

University Press, 1989.

Guth, Alan, and Steinshardt, Paul. “The Inflationary Uni-

verse.” In The New Physics, ed. Paul Davies. Cam-

bridge, UK: Cambridge University Press, 1989.

Kaku, Michio. “Gauge Field Theories.” In Quantum Uni-

fied Theory: A Modern Introduction. New York and

Oxford: Oxford University Press, 1993.

WILLIAM R. STOEGER

GRAVITATION

Gravitation is a universal attractive force exerted by

any two physical bodies on each other, even though

they may be separated by a large distance. Gravita-

tion is responsible for making objects fall to the sur-

face of the Earth (gravitational attraction of the ob-

ject by the Earth), for the nearly circular motions of

the planets around the sun (gravitational attraction

of the planets by the sun), for the structure of stars

and planets (gravitational attraction balanced by

pressure forces of constituent particles towards each

other), and for the structure of star clusters and

galaxies (hundreds of millions of stars would fly

apart from each other if not held together by grav-

ity). Gravitation also controls the rate at which the

universe expands, and is responsible for the growth

of small inhomogeneities in the expanding universe

into galaxies and clusters of galaxies.

Gravity is the weakest of the four fundamental

forces known to physics, but it dominates on large

scales because it is a long-distance force that is lo-

cally always attractive (in contrast to the far

stronger electromagnetic force, which can both at-

tract and repel, and cancels itself out on large

scales). Thus gravitation is a dominant force in

every day life, as well as in the motions of stars

and planets and in the evolution of the cosmos. In-

deed, it is one of the forces that makes our exis-

tence possible by enabling the formation and sta-

bility of plants like Earth that are hospitable to life.

Without gravity (at approximately the strength it

has on Earth) evolution of life would be difficult if

not impossible. This fact can naturally lead to spec-

ulation that the existence and specific nature of

gravitation could be part of a grand design allow-

ing self-assembling structures to come into exis-

tence and lead to intelligent life. In this way, grav-

ity can have theological significance.

Classical physics

Italian astronomer Galileo Galilei (1564–1642) first

recognized in the early seventeenth century that

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when air resistance can be neglected, objects ac-

celerate at the same rate towards the surface of the

earth, irrespective of their physical composition.

Thus a feather and a cannon ball will arrive at the

same time at the earth’s surface if simultaneously

released from rest at the same height in a vacuum

chamber. This means there is a universal rate of ac-

celeration downwards caused by the earth’s gravi-

tational field—approximately 32 feet per second

squared—irrespective of the nature of the object

considered. Gravitational potential energy can be

converted to kinetic energy, with total energy con-

served, as for example in a roller coaster or a pole

vaulter. This enables gravity to do useful work, as

in a clock driven by weights or a water mill, but it

also means people must work to go uphill. Gravity

can also be a danger to people, who can fall or be

hurt by falling objects. Despite this danger, gravity

is an essential part of the stability of every day

life—it is the reason that objects stay firmly rooted

on the ground rather than floating into the air.

In the late seventeenth century, Isaac Newton

(1642–1727) showed that the gravitational attrac-

tion of objects towards the earth and the motion of

the planets around the sun could be described ac-

curately by assuming a universal attractive force

between any two bodies, proportional to each of

their masses and to the inverse of the square of the

distance between them. The attractive nature of

gravity results because masses are always positive.

On this basis he was able to explain both the uni-

versal acceleration towards the surface of the earth

observed by Galileo and the laws of motion of

planets around the sun that had been observation-

ally established earlier in the century by Johannes

Kepler (1571–1630). This was the first major unifi-

cation of explanation attained in theoretical

physics, showing that two phenomena that initially

appeared completely unrelated had a unified ori-

gin. Newton’s account of gravitation also explained

why the direction of gravity varies at different

places on the surface of the earth (always being di-

rected towards its center), allowing “up” to be dif-

ferent directions at different places on the earth’s

surface (Australia and England, for example).

In conformity with the rest of theoretical

physics, Newton’s theory of gravity can be refor-

mulated as a variational principle (Hamilton’s prin-

ciple or Lagrange’s equations) based on minimisa-

tion of particular combinations of kinetic energy

and gravitational potential energy along the trajec-

tory followed by a particle. Gravity by itself is a

conservative theory (energy is conserved), so there

is no friction associated with the motion of stars

and planets in the sky, and their motion is fully re-

versible; the past and future directions of time are

indistinguishable, as far as gravity is concerned.

Newton was puzzled as to how the force of grav-

ity, as described by his equations, could succeed in

acting at a distance when there was no apparent

contact between the bodied concerned. Pierre

Laplace (1749-1827), a French physicist and math-

ematician, essentially resolved this puzzle by intro-

ducing the idea of a gravitational force field that

fills the empty space between massive bodies and

mediates the gravitational force between them. The

concept of such fields became one of the major

features of classical physics, particularly in the case

of electromagnetism. In quantum theory the idea

gravitational fields is revised and understood as

a force mediated by the interchange of force-

carrying particles.

Einstein and after

In the early twentieth century, Albert Einstein

(1879–1955) radically reshaped the understanding

of gravity through his proposal of the general the-

ory of relativity, based on the idea that space-time

is curved, with the space-time curvature deter-

mined by the matter in it. This theory predicts the

motion of planets round the sun more accurately

than Newtonian theory can, and also predicts radi-

cally new phenomena, in particular, black holes

and gravitational radiation. Insofar as science has

been able to test these predictions, they are correct.

A problem with the theory is that it predicts that

under many conditions (for example, at the start of

the universe and at the end of gravitational collapse

to form a black hole), space-time singularities will

occur. Scientists still do not properly understand

this phenomenon, but presumably it means that

they will have to take the effect of quantum theory

on gravity into account. General Relativity does not

do so; it is a purely classical theory.

Quantum gravity theories try to develop a the-

ory of gravity that generalizes Einstein’s theory and

is also compatible with quantum theory. Even the

way to start such a project is unclear. Approaches

include twistor theory, lattice theories, noncom-

mutative geometries, loop variable theories, and

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superstring theories. None has reached a satisfac-

torily developed state, however, much less been

tested and shown to be correct. Indeed, in many

ways such theories are likely to be untestable. The

most ambitious are the superstring theories, now

extended into a metatheory of uncertain nature

known as M-theory, which promises to provide a

unified theory of all fundamental forces and parti-

cles. M-theory still has far to go before making

good on that promise.

Despite the lack of a definite quantum theory

of gravity, various attempts have been made to de-

velop quantum theories of cosmology. These the-

ories also face considerable conceptual and calcu-

lational problems. The satisfactory unification of

quantum theory and general relativity theory, per-

haps in some unified theory of all the fundamental

forces, remains one of the most significant out-

standing problems of theoretical physics.

The desire to develop a practical antigravity

machine remains one of humanity’s outstanding

wishes. No present theory offers a way to such a

machine, but the negative gravitational effect of

the vacuum energy will continue to inspire some

to hope that one day such a machine might exist.

See also BLACK HOLES; COSMOLOGY, PHYSICAL

ASPECTS; FORCES OF NATURE; GALILEO GALILEI;

EWTON, ISAAC; PHYSICS, QUANTUM; QUANTUM

THEORY; RELATIVITY, GENERAL THEORY OF;

INGULARITY; STRING THEORY; SUPERSTRINGS

Bibliography

Begelman, Mitchell, and Rees, Martin. Gravity’s Fatal At-

traction: Black Holes in the Universe. New York: W.

H. Freeman, 1996.

D’Inverno, Ray. Introducing Einstein’s Relativity. Oxford:

Oxford University Press, 1996.

Ellis, George F. R., and Williams, Ruth M. Flat and Curved

Spacetimes. Oxford: Oxford University Press, 2000.

Hawking, Stephen W., Ellis, George F. R. The Large-scale

Structure of Spacetime. Cambridge, UK: Cambridge

University Press, 1973.

Misner, Charles W.; Thorne, Kip S.; and Wheeler, John A.

Gravitation. San Francisco: W. H. Freeman, 1973.

Thorne, Kip S. Black Holes and Time Warps. New York:

Norton, 1994.

GEORGE F. R. ELLIS

GREENHOUSE EFFECT

In the Earth’s atmosphere, there are five important

greenhouse gases that occur naturally: carbon

dioxide, methane, ozone, halocarbons, and nitrous

oxide. In correct proportion, these greenhouse

gases provide important protection for the Earth’s

surface. However, if the greenhouse gases become

too concentrated in the Earth’s atmosphere, then

they create a greenhouse effect that overheats the

Earth. Although a few scientists continue to dis-

sent, there is near unanimity among climatologists

that current global warming is caused by the dra-

matic increase in atmospheric carbon dioxide since

the advent of the Industrial Revolution and the ex-

traordinary increase in the combustion of fossil

fuels. In her essay, “The Greening of Science, The-

ology, and Ethics,” Audrey Chapman has argued

that ecological ethicists must understand the sci-

ence behind concepts such as the greenhouse ef-

fect in order to contribute meaningful ethical

analysis.

See also ECOLOGY; ECOLOGY, ETHICS OF; ECOLOGY,

ELIGIOUS AND PHILOSOPHICAL ASPECTS;

COLOGY, SCIENCE OF

Bibliography

Chapman, Audrey R. “The Greening of Science, Theology,

and Ethics.” In Science And Theology: The New Con-

sonance, ed. Ted Peters. Boulder, Colo.: Westview

Press, 1998.

RICHARD O. RANDOLPH

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