Journal of the American Scientific Affiliation 26 (1974) 61-64.
Copyright © 1974 by American Scientific Affiliation. Cited with permission.
The Levitical Dietary Laws
in the Light
of Modern Science
Thomas D. S. Key and Robert M. Allen
Thomas D.S. Key Robert M. Allen
Biology Dept Science Dept
Oglethorpe University Babb Junior High School
Atlanta, Georgia 30319 Forest Park, Georgia 30054
Leviticus 11 presents dietary laws, specifying which animals are "clean"
( edible) and "unclean" (inedible). Nine major theories to account for these
dietary laws are described in this paper, giving arguments pro and con regard-
ing each. The theories discussed are the Obedience Testing, Arbitrary Divine
Command, Assertion of Divine Authority, Moral Discipline, Hygiene, Spiritual
Symbolism, Pagan Worship, Religious Badge, and Eclectic theories.
The authors conclude that more evidence is needed, especially from
archaeology, to come to a definite conclusion regarding the validity of any of
these theories. They feel that if the original purpose of these dietary laws can
be determined, then perhaps we can make modern applications of lessons from them.
One of the most obvious characteristics of orthodox
conservative Jews as well as of Moslems and of the
Christian groups who emphasize the Old Testament is
the influence of the Levitical dietary laws on their
eating habits. Yet, when one questions those who
adhere to these dietary laws about the reasons for
them, he receives a variety of answers.
Leviticus 11 describes "clean" animals (i.e., those
which may be eaten) as follows: any animals that
“part the hoof, are cloven-footed, and that chew the
cud." Also, all aquatic animals that have fins and
scales, and winged insects that leap (i.e., locusts,
crickets, and grasshoppers) are "clean" or permitted
"Unclean" animals (i.e., those that are forbidden
for food) were listed as follows: camel, rock badger,
hare, swine, aquatic animals lacking fins and scales,
eagle, ossifrages, osprey, kite, falcon, raven, ostrich,
JOURNAL OF THE AMERICAN SCIENTIFIC AFFILIATION 61b
nighthawk, sea gull, hawk, owl, cormorant, ibis, water
hen, pelican, vulture, stork, heron, crawling insects,
hoopoe, weasel, mouse, great lizard, gecko, land croco-
dile, bat, lizard, sand lizard, and chameleon.
While the Bible nowhere states specifically why
the dietary laws were given, several theories have arisen
to account for them. Below are brief descriptions of
nine1 of these theories, along with some arguments for
and against their acceptance.
Obedience Testing Theory
This view asserts that the choice of animals was
arbitrary, but that God's purpose was to evaluate the
spirituality of the faithful. The obedience testing theory
also considers the Tree of Knowledge of Good and
Evil (Genesis 2) to have been arbitrarily selected,
and that it was the act of disobedience that imparted
the knowledge of good and evil rather than any physio-
logical effect of the chemicals present in the fruit.
Pro: The Scriptures indicate in several places where
the faith of people was tested (Job, I Kings 19, Gene-
sis 2 and 3, etc.).
Con: The choice of animals does not appear to be
arbitrary as the animals classified are consistent in
certain ways as discussed below.
Arbitrary Divine Command Theory
It seems strange to some that most strict adherents
of the Levitical dietary laws accept this theory, though
62a T. D. S. KEY AND R. M. ALLEN
they may not refer to it by this name. According to
this theory, the animals were arbitrarily classified by
God as clean or unclean with no specific reason what-
ever. We are told that to raise questions about the
reasons or advantages of these laws is to evade the
issue. We are to accept these laws by blind faith.
The point is that God commanded, and we are to obey.
“God said it. I believe it. And that settles it. Period."
Pro: If God had reasons for the laws, or if it were
important for us to know of them, they would have
been recorded. But such is not the case. The fact that
no reasons are given is evidence that they are unneces-
sary for us.
Con: It seems inconsistent with a loving, just,
omniscient God to be arbitrary, or to command just
for the sake of commanding. The fact that the animals
hold certain traits in common (shown in some of the
following theories) would tend to rule out the concept
that they were haphazardly or arbitrarily chosen.
Assertion of Divine Authority Theory
The purpose of these laws was to establish God's
authority, and to serve as a continual reminder of His
authority over and concern for His people, according
to this theory. These laws are beneficial in that they
tend to establish a habit of thinking frequently about
God and His place in our lives.
Pro: The concept of God's establishing His author-
ity and reminding others of it is certainly consistent
with many Scripture passages, for example, the re-
quiring of phylacteries, and redeeming each first-born
donkey with a lamb (Exodus -14); the Sabbath
(Exodus 20:8-11); the rainbow (Genesis -17);
stars (Genesis ); the mark on Cain (Genesis );
Miriam's leprosy (Numbers ); circumcision
(Genesis 17:11); and labor pangs, toil and thorns
(Genesis 3:17-19). The fact that no reasons are given
means none are needed. Reasons would weaken His
Con: The selection of animals would seem to in-
dicate that there was more to it than this (as indicated
in certain of the following theories). It would seem
arbitrary and superficial for God to assert His author-
ity in such an unproductive fashion. Would it not be
more profitable for God's kingdom and the spiritual
welfare of countless people if God required His people
JOURNAL OF THE AMERICAN SCIENTIFIC AFFILIATION 62b
to seek to win others to His ways? If God's purpose
for these laws is simply to assert His authority, why
would He not make useful laws, such as requiring the
faithful to be neighborly?
Moral Discipline Theory
According to this concept, the laws were to teach
moral discipline, much as it was once believed that
mathematics and Latin should be taught to discipline
the intellect. For similar reasons some military acade-
mies have required certain patterns of eating (i.e.,
special ways of holding silverware, of sitting erect
while eating, etc.) in order to remind cadets constantly
of their discipline.
Pro: The Bible is consistent with moral disciplinary
techniques. The fact that the price of a whore and of
a dog (Sodomite) were unclean tends to favor the
moral interpretation of these laws. In numerous pas-
sages the Hebrews were reminded that they "came up
out of the
laws would serve as similar daily reminders of their
moral discipline. Nazarites were to remain unshaved
and to abstain from alcohol for disciplinary reasons
(Numbers 6:2-20). Paul beat his body into subjection
(I Cor. 9:27). "The rod" is to be used for discipline
in certain circumstances (Proverbs ; ; and,
Con: As with the preceding theories, the particular
animals selected to be clean or unclean appear to have
enough in common to warrant other explanations than
this. To limit what foods may be eaten merely for
reasons of moral discipline, and to allow no exceptions,
could result in malnutrition, death, or forcing an im-
moral beaking of the laws in the event of famine,
poverty, or other problems.
The adherents of this theory point out that there
is close correlation between clean animals and those
that are less likely to transmit zoonoses (diseases
spread from animals to man), and between unclean
animals and those that are most likely to transmit
worms, bacteria, and other pathogens to man.
Pro: Hogs are particularly likely to spread disease,
e.g., trichinosis and Ascaris. Buzzards can transmit
many of the diseases that kill the animals on which
62c T. D. S. KEY AND R. M. ALLEN
they feed. Rat meat could give those who eat it
trichinosis and other diseases.
On the other hand, while cattle can give us tuber-
culosis, tapeworms, undulant fever, for example, they
are much less likely to give us more serious diseases.
Essentially the same can be said for sheep.
Any fish that "looks like a fish" is considered clean,
while oysters, clams, and other sea creatures are un-
clean. It is noteworthy here that true fish as a rule are
less likely to be
Not only does the hygiene theory account for the
particular selection of clean and unclean animals, but
also accounts for the listing of other unhygienic things
as unclean. For example, human wastes were unclean!
(Deut. 23:12-14), as well as cooking utensils and other
solid objects which were contaminated by people with
running sores (Leviticus and -55).
Paul wrote to Timothy that he should not drink
water, but should drink wine (I Timothy ). Paul's
reason obviously favors the hygiene theory, as water
was often polluted by human wastes, carcasses and
other bacteria sources.
Con: A much more sensible and practical regulation
would be to specify that all animals in sanitary environ-
ments are clean, while those that are raised in unsani-
tary environments are unclean. Or, better still, proper-
ly cooked meat is clean, while raw or rare meat is
unclean, regardless of the animal from which it comes.
If this were the regulation, not only could beef, mutton,
and true fishes be eaten without fear of zoonoses, but
the same would be true even of pork and other animals
listed as unclean. This theory also faces the difficulty
that unclean animals were let down from heaven to
Peter (Acts 10:9-29 and 11:5-12), and God responded
to Peter's refusal to eat with, "What God has cleansed,
you must not call unclean." The fact that menstruating
women and women who had just given birth were con-
sidered unclean (Leviticus 12), showed that the desig-
nation of unclean does not necessarily imply a poten-
tial source of contagion or infection. The fact that the
price of a whore or of a dog (or Sodomite) was un-
JOURNAL OF THE AMERICAN SCIENTIFIC AFFILIATION 63a
clean shows the same. Although there are numerous
poisonous plants, none is listed as unclean. And al-
though water could be polluted by carcasses, human
wastes, and other contaminants, nothing is discussed
regarding clean or unclean water. Even in those days
water was a main source of the spreading of disease.
Paul's advice to Timothy not to drink water was of
course written many centuries after the dietary laws
of Leviticus, and under the circumstances of Timothy
going on missionary journeys in which water could be
Some object to the Hygiene Theory on the grounds
that little was then known about hygiene, while others
insist that these hygiene laws prove divine inspiration.
(See also Matthew 15:11).
Spiritual Symbolism Theory
It is pointed out by those who favor this theory
that the clean animals have in common the fact that
they all symbolize spiritual virtues, while the unclean
animals symbolize spiritual vices.
Pro: It should be emphasized that the Bible is an
Oriental book, and that Orientals have long been noted
for symbolic and figurative speech. The Bible uses
several symbols for Christ: e.g., lamb (John ),
lion (Revelation 5:5), root (Revelation 5:5), and
grapevine (John 15: 1). The Holy Spirit is symbolized
by the dove (Luke 3), fire (Hebrews 12), and water
(Acts ). God,
bellious wicked, the Gospel, sin, and other persons
and concepts are represented by still other symbols, and
many of the symbols were animals. Cattle and oxen
are clean animals because they represent honest hard
work and obedience to duty. Donkeys are unclean as
they symbolize stubbornness, spiritual stupidity, and
selfishness. Snakes are unclean because they depict
Satan and sin (Genesis 3:1-15). Hogs are unclean
because they are greedy and look down. The horse is
unclean as it symbolizes pride and human military
Con: While the Spiritual Symbolism Theory is in-
triguing, it has some fatal inconsistencies. The lion is
unclean, yet it is used to represent Christ (Revelation
5:5) and the righteous (Proverbs 28:1). The pearl
represents the church (Matthew ), yet is pro-
duced by unclean clams and oysters. The symbolism in
63b T. D. S. KEY AND R. M. ALLEN
the Bible is not intended to be consistent and clear-
cut as this theory would assume. Thus, while doves
illustrate the Holy Spirit (Luke ), they also illus-
trate wicked Ephraim (Hosea ). The donkey is
an unclean animal, yet was chosen by Christ to ride
for His "triumphal entry" into
21). The serpent was a symbol of Satan, but was also
used for salvation (Numbers 21:9). Grapes are clean,
but their juice was warned against when it is fer-
mented (Ephesians 5:8 and I Timothy 3:3), and was
forbidden to Nazarites under most circumstances
(Numbers 6:3-20). The eagle is unclean, yet is used
to symbolize God's power (Revelation 4:7). The lion
is used to symbolize Christ (Revelation 5:5), Satan
(I Peter 5:8), the righteous (Proverbs 28:1), and the
rebellious wicked (Joel 1:6).
Pagan Worship Theory
It is noteworthy that the Hebrews spent centuries
living among neighbors who worshipped animal-like
gods. Part of the worship rites of these religions some-
While the Bible nowhere states spe-
cifically why the dietary laws were giv-
en, several theories have arisen to ac-
count for them. Given here are brief
descriptions of nine of these theories,
with arguments for and against their
times included the eating of these animals. Thus, the
sacred animals of these pagan religions were unclean,
while animals not sacred to these religions were clean.
Pro: The eagle was sacred to the Egyptians. The
snake, hawk, hog, goat, and horse were sacred to other
neighboring religions. Sheep, camels, true fish, and
most plants were not sacred to the nations and tribes
around the Hebrews, and hence were clean. The
faithful were to avoid all appearance of evil (I Thes-
salonians 5:22). They were forbidden to eat food
sacrificed to idols (Revelation , 20). It is inter-
esting that even today Arabs consider eating with
someone to be a close form of fellowship.
Con: Several plants were sacred to the pagan re-
ligions, but were not unclean (II Kings 23: 4). Cattle
were sacred to several groups (II Kings ), yet
JOURNAL OF THE AMERICAN SCIENTIFIC AFFILIATION 63c
were clean. There have long been fish gods and sea
gods, yet true fish were clean. In fact, fish deities are
more common than clam, oyster, or shrimp deities, yet
the fish were clean while the latter were not.
Religious Badge or Mark Theory
Many peoples have done or worn certain things to
distinguish themselves from others. The uniforms of
certain occupations are partly for this purpose, as are
some greetings, gestures, hairdos, and customs. The
Jews were God's earthly chosen people (Deuteronomy
7:6), chosen to witness for Him.
Pro: The Jews were required to do several things
as religious marks or badges to make them stand apart
as witnesses for God: circumcise their boy babies
(Genesis 17:10-27), rest on the Sabbath (Exodus
20:8-11), wear phylacteries on their foreheads (Exo-
dus ) and the like. The dietary laws were a log-
ical extension of these religious badges. The Bible
describes several other marks or badges of spiritual
significance. Paul was blinded on
the road to
to get Paul's attention and to show God's mark of
approval of Christ (Acts 9:3-9). Zechariah was struck
speechless for several days as a mark of God's relation-
ship to Christ's birth (Luke -23). Moses' sister,
Miriam, was marked with a whitish skin disease to
show God's disapproval of her objecting to Moses'
dark skinned African wife (Numbers 12:1-15). God
put a mark on Cain's forehead as a warning that no
one was to seek revenge against him (Genesis -
15). The Nazarites wore long hair and beards and ate
a strict diet (Numbers 6:1-21).
Con: The selection of clean and unclean animals
does not appear to be haphazard, but to fit certain
patterns (as discussed in some of the foregoing
theories). To prohibit certain wholesome foods merely
as religious badges could result in malnutrition or death
during famines. It could severely handicap the poor or
physically disabled. It could result in financial exploi-
64a T. D. S. KEY AND R. M. ALLEN
tation and monopolies of the few clean species. It
could result in upsetting the balance of nature due
to extermination of some species and the ignoring of
others. A more practical badge would appear to be
some kind of ritual associated with food preparation
Some Bible students prefer to combine parts of two
or more of the above theories to account for the reasons
behind the dietary laws. Actually, there are many vari-
ations of the eclectic theory. They obviously differ on
which of the above explanations are regarded as valid,
and to what extent the accepted explanations are con-
sidered to account for each animal.
Pro: The fact that the Bible does not indicate any
one reason might be due to the fact that several ex-
planations are necessary. The fact that several of the
preceding theories appear to be partially valid, yet
no one of them is capable of accounting for each an-
imal indicates that some eclectic explanation is neces-
sarily the correct one.
Con: It is difficult to evaluate the eclectic theory
as its variations are so numerous. Yet, the con argu-
ments for each of the preceding theories are sufficient
to show that none is valid as understood at present. If
all the links in a chain are weak, simply adding more
links will not make it stronger. Adding more straw to a
straw house does not make it more fireproof. Likewise,
simply adding useless theories together does not make
a valid explanation.
In the light of the above the authors conclude that
present evidence is not sufficient to warrant total ac-
ceptance of any one of the nine theories. More evidence
is needed, especially from possible future archaeological
discoveries. In the meantime, it would appear that, in
the light of the different kinds of dietary and other
"hygiene" laws given, that some eclectic interpretation
is probably correct.
It should be noted that many Christians feel that
it is no longer necessary to obey the Levitical dietary
laws as the Old Testament Law was our "schoolmaster"
to bring us to Christ (Galatians -25). Their in-
terest in them is primarily historical. Yet if we are
JOURNAL OF THE AMERICAN SCIENTIFIC AFFILIATION 64b
able to determine the original purpose of the laws,
perhaps we can make modern applications of lessons
from them. For this reason it is recommended that
further study be made on this subject.
l A tenth important theory was inadvertently omitted: the
Social Mores Theory. It argues that all societies have
certain customs and taboos, and that the dietary laws
are no more than this.
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Raymond M. An Illustrated Laboratory
Lapage, Geoffrey. Animals
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The United States Department of Agriculture, 1956.
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This material is cited with gracious permission from:
The American Scientific Affliation
report any errors to Ted Hildebrandt at: