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

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EXPERIENCE,RELIGIOUS:COGNITIVE AND NEUROPHYSIOLOGICAL ASPECTS

— 310—

unique state of consciousness different from nor-

mal waking and sleep. Unfortunately, EEG is lim-

ited in its ability to distinguish particular regions of

the brain that may have increased or decreased

activity.

For this reason, more recent studies of medita-

tion have used brain imaging techniques, such as

single photon emission computed tomography

(SPECT), positron emission tomography (PET), and

functional magnetic resonance imaging (fMRI).

Since about 1990, neuroimaging techniques have

been used to explore cerebral function during var-

ious behavioral, motor, and cognitive tasks. These

studies have helped to determine which parts of

the brain are responsible for a variety of neu-

rocognitive processes. These imaging techniques

have also allowed for the uncovering of complex

neural networks and cognitive modules that have

become a basis for cognitive neuroscience re-

search. Activation studies using these functional

neuroimaging techniques have helped researchers

determine the areas in the brain that are involved

in the production and understanding of language,

visual processing, and pain reception and sensa-

tion. In a typical activation study, the subject is

asked to perform such tasks as reading and prob-

lem solving while being scanned, and the activa-

tion state during the task is then compared to some

control state (usually resting). Since most spiritual

practices and their concomitant experience might

be considered from the perspective of an activa-

tion paradigm, functional brain imaging techniques

may be extremely useful in detecting neurophysi-

ological changes associated with those states. Re-

searchers can also use PET and SPECT to explore

a wide variety of neurotransmitter systems within

the brain. Neurotransmitter analogues have been

developed for almost every neurotransmitter sys-

tem, including the dopamine, benzodiazepine, opi-

ate, and cholinergic receptor systems.

There are limitations in each technique for the

study of meditation. It is important to ensure that

the technique is sensitive enough to measure the

changes. Also, each of these techniques may inter-

fere with the normal environment in which spiri-

tual practices take place. Early data of meditative

practices has generally shown increases in brain

activity in the region comprising the PFC, consis-

tent with focusing attention during meditation.

Studies have also observed decreases of activity in

the area of the PSPL, possibly consistent with inhi-

bition of sensory input into this area. However,

more studies, with improved methods will be nec-

essary to elucidate the neurocognitive aspects of

meditation and spiritual experiences. That the un-

derlying neurophysiology of extreme meditative

states can be considered at all allows for the con-

ceptualization of many other spiritual experiences

that lie along the spiritual continuum.

In all, these studies can provide a starting point

to develop a more detailed neurocognitive model

of religious and spiritual experience. This kind of

analysis can also be utilized as the hypothesis for

future investigations of such experiences.

See also CONSCIOUSNESS STUDIES; EXPERIENCE,

ELIGIOUS: PHILOSOPHICAL ASPECTS; MIND-BODY

THEORIES; MIND-BRAIN INTERACTION;

EUROSCIENCES

Bibliography

Bucke, Richard M. Cosmic Consciousness: A Study in the

Evolution of the Human Mind (1901). Secaucus, N.J.:

Citadel, 1961.

d’Aquili, Eugene G., and Newberg, Andrew B. “Religious

and Mystical States: A Neuropsychological Substrate.”

Zygon 28 (1993): 177–200.

d’Aquili, Eugene G., and Newberg, Andrew B. The Mysti-

cal Mind: Probing the Biology of Religious Experience.

Minneapolis, Minn.: Fortress, 1999.

Durkheim, Emile. The Elementary Forms of the Religious

Life: A Study in Religious Sociology (1915), trans.

Joseph Ward Swain. New York: Macmillan, 1926.

Eliade, Mircea. The Sacred and the Profane: The Nature of

Religion, trans. Willard R. Trask. New York: Harcourt,

1959.

Gellhorn, E. and Kiely, W.F. “Mystical States of Conscious-

ness: Neurophysiological and Clinical Aspects.” Jour-

nal of Nervous and Mental Diseases 154 (1972): 399-

405.

Joseph, Rhawn. Neuropsychology, Neuropsychiatry, and

Behavioral Neurology. New York: Plenum, 1996.

Newberg, Andrew B.; Alavi, Abass; Baime, Michael; Moz-

ley, P. David; and d’Aquili, Eugene. “The Measure-

ment of Regional Cerebral Blood Flow During the

Complex Cognitive Task of Meditation: A Preliminary

SPECT Study.” Psychiatry Research: Neuroimaging

106 (2001): 113–122.

Otto, Rudolph. The Idea of the Holy: An Inquiry into the

Non-rational Factor in the Idea of the Divine and its

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Relation to the Rational (1923), trans. John W. Har-

vey. New York: Oxford University Press, 1970.

Peng, C.K., Mietus J.E., Liu Y., et al. “Exaggerated Heart

Rate Oscillations During Two Meditation Tech-

niques.” International Journal of Cardiology 70

(1999): 101-107.

Smart, Ninian. Reasons and Faiths: An Investigation of Re-

ligious Discourse, Christian and Non-Christian. Lon-

don: Routledge and Kegan Paul, 1958.

Smart, Ninian. The Religious Experience of Mankind. Lon-

don: Macmillan, 1969.

Stace, Walter T. Mysticism and Philosophy. London:

Macmillan, 1960.

Streng, Frederick. “Language and Mystical Awareness.” In

Mysticism and Philosophical Analysis, ed. Steven

Katz. New York: Oxford University Press, 1978.

Turner, Victor. The Ritual Process: Structure and Anti-

Structure. Ithaca, N.Y.: Cornell University Press, 1969.

ANDREW B. NEWBERG

EXPERIENCE,RELIGIOUS:

HILOSOPHICAL ASPECTS

Although Protestants had previously used the

phrase religious experience as a rough synonym

for spiritual biography, William James (1842–1910)

first employed religious experience to denote a

generic category, applicable to all religions and

susceptible to scientific analysis. James’s The Vari-

eties of Religious Experience (1902) gave the new

category a broad extension. He described his topic

as “personal religion in the inward sense,” con-

trasted with institutional religion and theology

(p. 42). From a psychological standpoint James

aimed to provide a “descriptive survey of the reli-

gious propensities” (p. 22), including religious feel-

ings and emotions, religious impulses, religious

motivations, and nonritualized religious actions.

James’s methodological decision to focus on the

extreme expressions of personal religion exhibited

by “religious geniuses” (p. 24) has contributed to

a tendency to narrow the category of religious ex-

perience to include primarily extraordinary,

paranormal experiences and mystical states of

consciousness.

With his “descriptive survey of the religious

propensities,” James hoped to contribute to a “Sci-

ence of Religions” as he conceived it. His Science

of Religions would distill the beliefs of various re-

ligions until they harmonized with each other, and

then formulate hypotheses that reconciled this uni-

versal content with the rest of science. James iden-

tified as common to religions the consciousness of

something “more” that is continuous with the

higher part of oneself. To render this generalized

religious content palatable to science, he invoked

the subconscious. He hypothesized that “whatever

it may be on its farther side, the ‘more’ with which

in religious experience we feel ourselves con-

nected is on its hither side the subconscious con-

tinuation of our conscious life” (p. 386). James be-

lieved that a Science of Religions would commend

itself to believer and scientist alike, and could

prove as credible as the natural sciences. Though

others too have hoped to reconcile science and re-

ligious experience, few have entertained so san-

guine an expectation.

An early theory

Despite the fact that James adopted the term reli-

gious experience at the turn of the twentieth cen-

tury, the scientific interest in what James and later

thinkers would call religious experience dates to

the eighteenth century. David Hume’s (1711–1776)

essay “Of Superstition and Enthusiasm” (1741) rep-

resents one of the earliest psychological explana-

tions of religious experience. It attempts, more-

over, a sociology of religious experience. With

the notable exception of Emile Durkheim’s

(1858–1917) The Elementary Forms of Religious Life

(1912), most later theories focus exclusively on ei-

ther the psychology of religious experience or the

sociology of religious experience—its social deter-

minants and social uses. Hume wanted to establish

general principles with which to explain human

nature (moral philosophy) in the same way that

Newton had established general principles with

which to explain physical nature (natural philoso-

phy). Hume drew on his science of human nature

to explain religion. Superstition and enthusiasm,

he argued, represent different implicit explanations

of anomalous emotional states. A superstitious per-

son, ignorant of the physiological cause of object-

less fear, attributes it to the existence of invisible

malevolent beings who require appeasement

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through rites and mortifications. An enthusiast, by

contrast, ignorant of the physiological cause of un-

warranted hope or pride, attributes it to divine in-

spiration and experiences transports, raptures, and

ecstasies. In both cases the subject resorts to imag-

inary causes to satisfy an explanatory interest.

Hume believed that the proportions of super-

stition and enthusiasm in a religion had important

social consequences. He argued that superstition

requires priests to interpose on behalf of the

cowed fearful, whereas enthusiasm will not abide

priests because the enthusiast believes his sacred

commerce with God obviates institutions and their

representatives. Enthusiastic religions begin tumul-

tuously, even violently, but quickly moderate be-

cause their weak institutional structure cannot sus-

tain the fervor. Nevertheless, enthusiasm’s spirit of

self-reliance and autonomy bolsters civil liberty.

Superstition, by contrast, gains ground gradually

by taming its adherents and ends in tyranny. De-

spite the fact that Hume emphasizes only the in-

fluence an individual’s emotions have on his reli-

gion and overlooks the extent to which the

doctrines of a religion inform the quality of the in-

dividual’s emotions, his account is superior to

many later theories for at least one major reason.

Hume stresses the cognitive nature of religious ex-

perience, that explanatory commitments are con-

stitutive of religious experience. The subject’s own

tacit or implicit commitments about the proper ex-

planation of the experience are what makes the

experience the experience it is. Many later theo-

rists, including James, elide this feature of religious

experience.

Polemics and apologetics

Hume’s theory had a polemical tenor. He labeled

both superstition and enthusiasm “species of false

religion” (p. 73), and the essay has a political sub-

text. Hume is instructive in this regard. The study

of religious experience, like the study of religion it-

self, had its origin in polemics and apologetics.

This history explains the contours of the concept.

Religious experience was forged in response to the

modern challenge to religion. Since the Enlighten-

ment, rational inquiry had impugned the traditional

sources of religious knowledge. Baruch Spinoza

(1632–1677) and the subsequent development of

higher textual criticism undermined scriptural au-

thority. The creation of modern probability theory

eroded the once intrinsic connection between doc-

trinal authority and credibility. Hume and Im-

manuel Kant (1724–1804) effectively thwarted the

aspiration for natural theology, while Hume, fur-

thermore, produced what he called a “check”

against the credibility of miracle claims. By way of

rejoinder, apologists turned to spiritual or mystical

experience as a ground for religious commitment.

They argued that religious experience is cogni-

tively immediate (i.e., not influenced by, or a prod-

uct of, prior beliefs) and, therefore, unassailable by

rational and historical inquiry into the defensibility

of religious beliefs. If religious experience were, in

part, a product of prior religious beliefs, one could

not use religious experience as an independent

ground for religious commitment. Armed with this

understanding of religious experience, the increas-

ing exposure to the vast diversity of religions pre-

sented not a challenge, but a defense in numbers.

Despite incompatible beliefs and practices, all reli-

gions at bottom stem from the same or similar ex-

periences, feelings, or sentiments.

Friedrich Schleiermacher (1768–1834) inaugu-

rated this apologetic conception of religious expe-

rience. In On Religion: Speeches to its Cultured De-

spisers (1799) he explained that religion consists in

piety, a distinct moment of consciousness that he

construed as “a sense or taste for the Infinite.” In his

later systematic theology, The Christian Faith

(1830) he described piety as the “feeling of absolute

dependence” that accompanies all self-conscious-

ness. In both works he sharply distinguished piety

from belief and insisted on the immediacy of piety.

Ultimately, he heralded an “eternal covenant” be-

tween science and religion, whereby religion al-

lows to science all that is of interest to it (1981, pp.

64–65). The immediate, noncognitive nature of

piety, he claimed, eliminated the possibility of a

conflict. The tendency to treat religious experience

as immediate and to consider it the source of reli-

gion became widespread after Schleiermacher. De-

spite James’s refusal to distinguish sharply between

feelings and beliefs in his more psychological and

philosophical works, he too displays this tendency

in The Varieties of Religious Experience when he

claims that personal religious feelings are immedi-

ate, primordial, and ultimately productive of beliefs.

Naturalistic explanations of religious experi-

ence, such as Hume’s, had their effect on the con-

cept of religious experience as well. Ann Taves, in

her book Fits, Trances, and Visions (1999) has

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shown how American religious groups, especially

among the elite, tended to construct their notions

of genuine religious experience by contrasting it

with experiences that could be explained natura-

listically. Furthermore, they often adopted the nat-

uralistic explanations for experiences they wished

to discourage. In the eighteenth century, for in-

stance, Jonathan Edwards (1703–1758), the Calvin-

ist divine, distinguished in his mature writings be-

tween genuine religious affections and enthusiasm,

the latter involving “imaginary ideas . . . strongly

impressed upon the mind” (Taves, p. 39). In the

nineteenth century, religious explanations of reli-

gious experience continued to compete with natu-

ralistic explanations, now phrased in terms of mes-

merism. Seventh Day Adventists and Christian

Scientists explained false religion by invoking mes-

merism, while mainline denominations tended

likewise to dismiss the experiences of Adventists

and Christian Scientists as products of mesmerism.

Some religious movements, such as Spiritualism,

embraced mesmerism as a natural and sufficient

means for attaining access to the spirit world and,

therefore, attempted a form of religious naturalism.

Taves’s work demonstrates that thought about reli-

gious experience has implicitly been thought about

naturalistic explanation as well.

The polemical and apologetic history inform-

ing the concept of religious experience has shaped

its connotation. The concept suggests ethereal ex-

periences like those that have come to be called

mystical because these states seem more resistant

to naturalistic explanation, more plausibly immedi-

ate, and more promising as a ground for religious

commitment than somatic automatisms or vision-

ary experience. The latter seem pathological and

best explained naturalistically. James’s ultimately

unsuccessful labors to neutralize “the bugaboo of

morbid origin” in the very first chapter of The Va-

rieties of Religious Experience, before even defining

his topic, reflects this concern to hedge religious

experience from pathology (p. 35). The insistence

in many mystical texts on ineffability—that the ex-

perience cannot be described—has lead many to

consider mystical states of consciousness the para-

digmatic religious experiences. Ineffability is taken

to signal immediacy. The modern interest in reli-

gious experience has frequently led to interpretive

mistakes. Some religious thinkers engaged in neg-

ative theology, such as Pseudo-Dionysius, who as-

sert the ineffability of its conclusions, have been

mistakenly read as describing altered states of con-

sciousness.

Contextualists and perennialists

The alleged immediacy of mystical states continues

to be a point of controversy in the study of reli-

gious experience. So-called contextualists or con-

structivists follow in Hume’s footsteps. They argue

for the cognitive nature of religious experience. In

Religious Experience (1985) Wayne Proudfoot ar-

gued on logical grounds that the subject’s implicit

explanation of their experience in religious terms

makes their experience a religious experience. The

commitments the subject harbors about the causes

of their experience and the terms appropriate to

describe it are constitutive of the experience. They

determine its intentionality, or what the experience

is of. For this reason subjects who adopt commit-

ments derived from different religious traditions

have different experiences. Proudfoot argues,

moreover, that one should not understand the in-

effability reported in mysticism as an unanalyzable,

descriptive characteristic of experience indicating

its immediacy but rather as a feature of the theo-

logical concepts and commitments informing the

intentionality of the experience.

So-called perennialists follow in Schleierma-

cher’s footsteps. They argue for the immediacy of

certain forms of religious experience. Robert For-

man has argued largely on phenomenological

grounds for the existence of states of wakeful, non-

intentional consciousness. He calls episodes of this

state of contentless consciousness Pure Conscious-

ness Events (PCEs). They are nonintentional be-

cause they are not experiences of anything. For-

man sees evidence of PCEs in a number of

meditative traditions around the world. Because

PCEs have no content, he claims, they cannot be

culturally specific. Mystics of any tradition achiev-

ing PCEs have the qualitatively identical ineffable

experience. Contextualists reply that the textual ev-

idence adduced by perennialists does not support

the assertion of a cross-cultural uniformity of ex-

perience. They also argue that phenomenological

descriptions of what feels like contentless con-

sciousness do not necessarily mean that the expe-

riences are immediate (i.e., unconditioned by prior

beliefs). Regardless, one should note that even if

Forman has indeed identified a form of content-

less, immediate consciousness, that fact has no in-

trinsic religious significance. Religious significance

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could only come ex post facto from interpretation.

Because PCEs have no intrinsic religious import,

they cannot by themselves serve the apologetic

motivations that inspire the search for immediate

experience.

Neuroscience

Advances in neurobiology have fostered the hope

that a better understanding of the brain can explain

religious experience. For some scholars brain func-

tion (or malfunction) provides models for accounts

of extraordinary religious states. Michael Persinger,

for instance, observes the similarities between the

psychological effects produced by temporal lobe

epilepsy and what he calls “God Experiences.” On

this basis and with no intention of stigmatizing reli-

gion, he infers that transient electrical microseizures

in the temporal lobe of the brain explain “God Ex-

periences.” Eugene d’Aquili and Andrew Newberg

offer a different neurological explanation of reli-

gious experience. They provide a complex model

whereby ritual and meditation, by different routes,

lead to the activation of the autonomic nervous sys-

tem. This stimulation, in conjunction with the sub-

sequent activation of some and isolation of other

higher brain areas, creates various forms of religious

experience, including contentless mystical states of

Absolute Unitary Being (AUB). Like Schleiermacher

and James, they view religious experience as the

source of theology and institutions. They maintain

that these circuits of neurophysiological stimulation,

which affect areas of the brain responsible for

causal and holistic cognition, produce religious con-

cepts and even mystical traditions. D’Aquili and

Newberg’s theory is generally considered highly

speculative. It also slights the cognitive dimension

of religious experience. The physiological under-

pinning or component of experience does not suf-

fice to make an experience a religious experience.

The subject’s implicit commitment to a religious ex-

planation of the experience makes an experience a

religious experience. To this extent a social or cul-

tural explanation of religious experience is neces-

sary. Neurology by itself is insufficient.

See also CONSCIOUSNESS STUDIES; EXPERIENCE,

ELIGIOUS: COGNITIVE AND NEUROPHYSIOLOGICAL

ASPECTS; HUME, DAVID; MIND-BODY THEORIES;

IND-BRAIN INTERACTION; MYSTICISM;

EUROSCIENCES; PSYCHOLOGY OF RELIGION;

OCIOLOGY

Bibliography

Bagger, Matthew. Religious Experience, Justification, and

History. Cambridge: Cambridge University Press, 1999.

D’Aquili, Eugene, and Newberg, Andrew. The Mystical

Mind: Probing the Biology of Religious Experience.

Minneapolis, Minn.: Fortress Press, 1999.

Durkheim, Emile. The Elementary Forms of Religious Life

(1912), trans. Karen Fields. New York: Free Press,

1995.

Forman, Robert, ed. The Problem of Pure Consciousness:

Mysticism and Philosophy. New York: Oxford Univer-

sity Press, 1990.

Forman, Robert, ed. The Innate Capacity: Mysticism, Psy-

chology, and Philosophy. New York: Oxford Univer-

sity Press, 1998.

Hume, David. “Of Superstition and Enthusiasm” (1741). In

Essays: Moral, Political, and Literary. Indianapolis,

Ind: Liberty Fund, 1985.

James, William. The Varieties of Religious Experience

(1902). New York: Mentor Books, 1958.

Katz, Steven, ed. Mysticism and Philosophical Analysis.

New York: Oxford University Press, 1978.

Katz, Steven, ed. Mysticism and Religious Traditions. New

York: Oxford University Press, 1983.

Lewis, I. M. Ecstatic Religion: A Study of Spirit Possession

and Shamanism, 2nd edition. London: Routledge,

1988.

Persinger, Michael. Neuropsychological Bases of God Be-

liefs. New York: Praeger, 1987.

Proudfoot, Wayne. Religious Experience. Berkeley: Univer-

sity of California Press, 1985.

Schleiermacher, Friedrich. The Christian Faith (1830),

trans. H. R. Mackintosh and J. S. Stewart. Edinburgh,

UK: T&T Clark, 1928.

Schleiermacher, Friedrich. On the Glaubenslehre: Two

Letters to Dr. Lucke (1829), trans. James Duke and

Francis Fiorenza. Chico, Calif.: Scholars Press,

1981.

Schleiermacher, Friedrich. On Religion: Speeches to its Cul-

tured Despisers (1799), trans. Richard Crouter. Cam-

bridge, UK: Cambridge University Press, 1996.

Taves, Ann. Fits, Trances, and Visions: Experiencing Reli-

gion and Explaining Experience from Wesley to James.

Princeton, N.J.: Princeton University Press, 1999.

MATTHEW C. BAGGER

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EXPLANATION

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EXPLANATION

When one wants to understand something, one asks

for an explanation. In principle, everything can be

the object of explanation. Some explanations, such

as in classification and interpretation, explain what

something is: What is a whale? It is a mammal;

Could you explain the movie Dr. Strangelove to me?

It is about the Cold War. Some explanations explain

how something works or how something is possi-

ble: How does the door open? Press the button;

How is it possible that some children survive the

most cruel experiences? There are adults who love

them and care about them. Finally, some explana-

tions explain why something happens: Why did the

aircraft crash? Because one of its motors came loose.

In all three cases, the explanation is supposed to

yield knowledge. Concerning the why-questions,

however, not all are requests for an explanation

and, thus, not every answer to a why-question

yields knowledge. Some why-questions express the

wish to find consolation (Why have you abandoned

me?) or the wish to get rid of prejudices (Why

should men and women not get the same salary for

the same job?). In the science and religion discus-

sion it is intensely debated whether religious an-

swers to such a question as “Why is the universe so

special and finely tuned for life?” are explanations,

yielding knowledge, or whether they have other

functions in the believer’s life.

The covering law model

Quite often explanations of why something is the

case are related to causation. Other explanations

are functional or teleological, as they are also

called. The white fur of the polar bear is explained

by its camouflage function. A common view is that

those explanations actually are causal explanations

referring to past causes in evolution that led to the

natural selection of the biological trait in question.

Causal and functional or teleological explanations

are seen as two different variants of the so-called

covering law model.

According to the covering law model, an ex-

planation of an event consists in subsuming it

under a causal law: All metals expand when

heated; this rod is metallic and it was heated;

therefore, it expanded. There are four conditions

for such a scientific explanation:

(1) The explanandum (The rod has expanded.)

has to follow logically from the explanans

(All metals expand when heated; this rod is

metallic and it was heated.). Only if the ex-

planandum can be deduced from the initial

circumstances and the applied causal laws,

the explanandum is really explained and jus-

tifies the prediction of a similar event, even if

it has not been observed yet.

(2) The applied causal laws (All metals expand

when heated.) have to be laws proper and

not only all-statements. It is not an explana-

tion to say: “All apples in this basket are red;

this apple is from the basket; therefore, the

apple is red.”

(3) The explanans needs to have empirical con-

tent; it should be possible, at least in princi-

ple, to confirm or falsify the explanans

through experience. Without this condition

explanations like God’s wrath as the cause of

historical catastrophes could not be excluded

from science.

(4) The explanans has to be true. If it were false,

the implication between the explanans and

any explanandum would be true for logical

reasons and the explanandum would not be

explained.

Although the covering law model cannot be

applied everywhere in its strict form, it is supposed

to represent an ideal that at least all explanations in

the natural sciences that are answers to why-ques-

tions ought to strive to attain. It satisfies one fea-

ture that one would expect of such explanations,

namely, that it explain why a certain event oc-

curred and not another. By subsuming an event

under causal laws, it is shown that the event had to

occur. The price to be paid for this is determinism,

excluding the possibility of exceptions. One way

of coping with this difficulty is to allow determin-

istic as well as nondeterministic explanations.

Thus, the explanation of a patient’s death from

lung cancer may take the form of a statistical ex-

planation referring to the frequency of dying from

lung cancer and smoking heavily. According to this

variant of the covering law model, the explanan-

dum is not deduced from the explanans. It is sup-

posed to follow with an inductive probability. The

reference is not to exceptionless laws but to statis-

tical regularities concerning events and to tenden-

cies concerning human actions.

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EXTINCTION

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Rational reconstruction

Another model of explanation that is supposed to

be an alternative to the covering law model in, for

instance, historical research consists in explaining

an event as the result of human action by rational

reconstruction. First, an event is shown to be an in-

tentional act that the agent in question has under-

taken in accordance with beliefs that seemed rea-

sonable in the situation at issue. Second, the

critical examination of the agent’s beliefs, whether

true or reasonable, contributes to explain why the

action resulted in precisely that event. So, in some

historical cases, the fact that the belief in the

enemy’s strength was false may explain why the

army was defeated in a certain battle.

Explanation in the science-religion dialogue

One frequently discussed question in theology and

in philosophy of religion concerns the relationship

between scientific and religious explanations:

whether they are on the same categorical level or

belong to completely different domains. The differ-

ence between scientific and religious explanations

is sometimes identified by pointing out that science

causes questions that go beyond its own power to

answer, for instance, the question “Why is the uni-

verse so special and finely tuned for life?” Since this

question is not a question formed within science, it

cannot be answered scientifically. Instead, the

question is a metaphysical why-question, where-

fore it can be answered, for instance, theistically by

saying “because the universe is created by God

who wills that it be so.” Since it is not always clear

to what extent cosmological theories about the be-

ginning of the universe are metaphysically laden, it

is also not clear to what extent the theistic answer

competes with scientific explanations or with the

metaphysical aspects of some of these theories.

See also CAUSALITY, PRIMARY AND SECONDARY;

AUSATION

Bibliography

Clayton, Philip D. Explanations from Physics to Theology:

An Essay in Rationality and Religion. New Haven,

Conn.: Yale University Press, 1989.

Collingwood, Robin George. The Idea of History, rev.

edition. Oxford: Clarendon Press, 1993.

Dray, William H. Laws and Explanation in History. Ox-

ford: Oxford University Press, 1957.

Gregersen, Niels Henrik, and van Huyssteen, J. Wentzel,

eds. Rethinking Theology and Science: Six Models for

the Current Dialogue. Grand Rapids, Mich.: Eerd-

mans, 1998.

Hempel, Carl G. Aspects of Scientific Explanation and

Other Essays in the Philosophy of Science. New York:

Free Press, 1965.

Polkinghorne, John Charlton. Quarks, Chaos, and Chris-

tianity: Questions to Science and Religion. London:

Triangle, 1994.

van Fraassen, Bas C. The Scientific Image. Oxford: Claren-

don Press, 1980.

von Wright, Georg Henrik. Explanation and Understand-

ing. London: Routledge and Kegan Paul, 1971.

EBERHARD HERRMANN

EXTINCTION

See EVOLUTION

EXTRATERRESTRIAL LIFE

The concept of extraterrestrial life, embodied in

the discipline known as exobiology, astrobiology,

or bioastronomy, is one of the oldest in the history

of science. Although the search for life beyond

Earth has always been intrinsically difficult, and in-

termingled with philosophy and theology, it has

usually been a reflection of the science of its times.

The idea of an infinite number of worlds was

part of the ancient Greek atomist system, but was

opposed by the physical principles of the philoso-

pher Aristotle. Beginning in the sixteenth century,

Copernican theory made the Earth a planet, and the

other planets potential Earths. In the seventeenth

and eighteenth centuries, Cartesian cosmology ex-

tended the idea to other planetary systems, as did

Newtonian cosmology, at first in conjunction with

natural theology and later with the nebular hypoth-

esis. Only in the twentieth century, and especially

with the space age, has empiricism become a major

component of the search for extraterrestrial life. It

has done so under the banner of cosmic evolution,

the idea that the universe has evolved from the Big

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Bang to planets, stars, galaxies, life, and intelli-

gence. Although at the limits of science, the ques-

tion of the abundance of life in the universe has

been passionately pursued because it bears so

strongly on humanity’s place in the universe. As

such, “the biological universe,” as it has been

called, has generated considerable and ever in-

creasing theological and philosophical discussion.

Research on extraterrestrial life

Research on extraterrestrial life is pursued in at

least four areas: planetary science, planetary sys-

tems science, origins of life studies, and the Search

for Extraterrestrial Intelligence (SETI). Not surpris-

ingly, the planet Mars was the focus for much of

the twentieth century, beginning with the canals of

Mars controversy and culminating with the Viking

missions in 1976. The latter demonstrated to the

satisfaction of most scientists that no organic mol-

ecules were present on the surface of Mars at the

Viking lander sites, samples of which were ana-

lyzed down to parts per billion. Surprisingly, the

problem of life on Mars was again highlighted in

1996 when scientists at NASA announced possible

fossils in an ancient Mars rock found in the Antarc-

tic. This conclusion caused an uproar and is still

hotly debated. Meanwhile, the discovery of a pos-

sible liquid ocean under the ice of the Jovian moon

Europa raised the unexpected possibility of life in

the solar system beyond the ecosphere usually

considered hospitable for life.

Although Earth-like conditions have not been

found elsewhere in the solar system, extrasolar

planets provide potential abodes of life. After a

long and fruitless search during most of the twen-

tieth century, in 1995 the first planet was found

around the solar-type star 51 Pegasi. In the follow-

ing six years, with increasingly refined technology,

more than eighty planets were found around sun-

like stars within a few hundred light years of Earth.

More are being discovered monthly. The evidence

is indirect, and the planets discovered through

2001 are gas giants like Jupiter, many in highly ec-

centric orbits or very close to their parent stars. The

search continues for Earth-size planets, and the

technology is advancing to the point where their

detection may be possible within the next decade.

Because there is no guarantee that life will

arise even on Earth-like planets, an understanding

of the mechanisms of the origin of life is essential.

Unfortunately, these mechanisms are not well un-

derstood, even on Earth. Nevertheless, the discov-

ery of life in extreme environments—inside rocks,

several kilometers below the surface of the Earth,

and deep in the ocean—indicates that extraterres-

trial life might develop under conditions consider-

ably broader than thought possible. In particular,

the exploration of deep-sea hydrothermal vents

and their associated life, including tube worms sev-

eral meters in length, has provided insights into the

limits of life, and even the possible origin of life on

Earth. Delivery of organic materials, and even life,

from beyond the Earth remains an alternative pos-

sibility for the origin of life.

SETI programs seek artificial signals emanating

from planets around sun-like stars, using a variety

of assumptions about signal frequency and targets.

For forty years, beginning with Frank Drake’s Pro-

ject Ozma in 1960, SETI relied mainly on radio tel-

escope technology. During the 1990s, the search

began expanding to include optical techniques,

even as dedicated facilities were being built and in-

creasingly complex software constructed for signal

detection. While there have been some false

alarms, no unambiguous signals from extraterres-

trial intelligence have been detected. In fact, aside

from the controversial Mars rock, no form of ex-

traterrestrial life has yet been discovered.

Implications for religion and humanity

The human implications of the existence of extra-

terrestrial life have almost always been discussed in

terms of extraterrestrial intelligence. For centuries

religious implications have been a center of atten-

tion, especially in the Christian context, beginning

with medieval commentaries on Aristotle and in-

creasing significantly in the wake of heliocentrism.

In the post-Newtonian era, scriptural objections

were largely met by demonstrations of the benefits

of extraterrestrials to natural theology, in which a

universe full of life was seen as a demonstration of

God’s omnipotence and the magnificence of divine

creation. During the nineteenth century, in the ab-

sence of techniques to resolve the scientific ques-

tion of life on other worlds, the religious implica-

tions were explored in considerable detail. Three

options were considered and adopted: religion and

extraterrestrial life could be reconciled, certain reli-

gious doctrines could be rejected, or the idea of in-

habited worlds could be rejected. No consensus

has been reached on these options. Nor is there

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consensus on the effect of the discovery of extra-

terrestrials on Christian thought, particularly the

doctrines of redemption, incarnation, and salvation.

A few religions, including Mormonism, have incor-

porated the concept of life on other worlds into

their religious doctrine. The implications for non-

Western religions have only begun to be explored,

but in general it seems that the effect on non-

Adamist religions would be less than on those that

teach salvation through a single God-head.

In a broader sense, the biological universe may

be seen as a worldview analogous to the Coperni-

can and Darwinian worldviews. It is possible that

the implications for humanity will be similarly

widespread, and may follow the general outlines of

the reception of past world views, for which there

is a rich literature in the history of science. Science

fiction, both literature and film, has also addressed

the human implications. In particular the work of

Olaf Stapledon, Arthur C. Clarke, Stanislaw Lem,

Carl Sagan, and Maria Dorrit Russell, have treated

the theme of alien life in a thoughtful manner.

Finally, extraterrestrial intelligence may relegate

all human knowledge to the status of a specific in-

stance of a more general knowledge possessed, and

perhaps shared, by civilizations scattered through-

out the universe. On the other hand, in the absence

of extraterrestrial intelligence, human destiny may

be to spread throughout the galaxy on some varia-

tion of the model adopted in Isaac Asimov’s Foun-

dation series of novels, as opposed to the complex

interactions with extraterrestrials found in Clarke’s

work. Either way, the implications are sobering.