The History of Natural Law
The origins of natural law lie in the thought
of the philosophers and jurists of the ancient world. They were convinced
that there were rules for human behavior based upon objective, eternal norms.
They conceived of these norms as having been established by nature and reason.
The Romans were the first to coin the term “natural law”(ius naturale).
Medieval jurists and theologians found the idea of natural law attractive.
It was congruent with their conception of the universe and with their notions
of human psychology. Expanding upon and developing further the definitions
of natural law they found in the ancient sources, medieval jurists and
theologians placed natural law at the pinnacle of a hierarchy of laws that
regulated and guided human behavior. Their paradigm held sway in western
jurisprudence until the nineteenth century.
The Roman orator Cicero († 43 B.C.) summed up an important strand of
ancient thought when he argued in his De republica 3.22 that “true law
was right reason that was congruent with nature.” He concluded that
“there was one eternal, immutable, and unchangeable law” and that
God had established it as the Emperor and Master of all humankind. Later
Christian thinkers incorporated Cicero’s conception of law into their
own thought. The ancient Roman jurists dealt with two types of law that
transcended the law of the Roman Empire, the law of peoples (or nations)
(Ius gentium) and natural law (Ius naturale). In the second century A.D.
the Roman jurist Gaius was the first to define the Ius gentium as having
been established by the natural reason of all humankind (Institutes 1.1).
Later jurists did not always distinguish carefully between natural law and
the Ius gentium. This conceptual ambiguity would long remain a problem of
jurisprudential and theological thought. In the third century the jurist
Ulpian defined natural law as what “nature teaches all animals,”
including human beings. He distinguished natural law from the Ius gentium
that was common only to human beings and established by their customary usages.
He cited marriage and the procreation of children as examples of natural
law. Ulpian’s definition was later included in the Emperor Justinian’s
comprehensive codification (ca. 533-536) of Roman law (Digest 1.1.3).
Justinian’s codification also included a introductory textbook for the
study of law called the Institutes. The definition of natural law in the
Institutes moved the source of natural law from the behavior of creatures
to God: “Natural laws are established by divine providence and always
remain firm and immutable (Institutes 1.2.11).” A little later the authors
of the Institutes asserted that the Ius gentium is identical with natural
law (Institutes 2.1.11). In every European law school from the eleventh to
the seventeenth century, professors and students studied and pondered
Ulpian’s and the Institute’s definitions — and their
contradictions.
Although some late antique Christian theologians mentioned natural law in
their writings, they did so infrequently. Natural law never became an important
concept in the theological thought of the early church fathers. When Isidore
of Seville composed (ca. 620) his encyclopedic Etymologies (5.4) he combined
the two traditions that had circulated in the ancient world. He defined natural
law as being the law common to all nations that was established by the
instigation (instinctus) of nature, not by human legislation. Examples of
natural law were marriage and the procreation of children, “one liberty
of all human beings (una libertas omnium),” and the acquisition of property
taken from the heavens, earth, and sea.
From Isidore to the jurist Gratian in the twelfth century there was virtually
no discussion of natural law as a norm for human society. As part of his
plan to bring order to the chaotic state of church law, Gratian(ca. 1140)
compiled a legal collection of ecclesiastical norms. At the beginning of
his canonical collection, called the Decretum, he discussed the various types
of laws that regulated and guided the behavior of human beings. In the opening
sentence of his collection Gratian brought natural law to the forefront of
all future discussions about the structure of all human law: “The human
race is ruled by two things, namely, natural law and customary usages. Natural
law is what is contained in the law (lex sic) and Gospels.” Gratian
concluded that natural law dictated that “Each person is commanded to
do to others what he wants done to himself,” connecting natural law
with the biblical injunction to do unto others what you would have them do
unto you (Matthew 7.12). By defining natural law as the duty to treat other
human beings with care and dignity, Gratian stimulated jurists to reflect
upon a central values of natural law: the rendering of justice and the
administering of equity in the legal system. To define the contents of natural
law he placed Isidore’s definition of natural law on the first page
of his Decretum (D.1 c.7). Together with the texts of Roman law in
Justinian’s compilation, Gratian’s Decretum became one of the standard
introductory texts for the study of law (the Ius commune) in European law
schools, and Isidore’s definition became one of the most important starting
points for all medieval discussions of natural law.
Medieval jurists and theologians found several natural laws in their sources.
During the twelfth century when the jurists subjected these definitions of
natural law to careful analysis, they brought out these contradictions. They
pointed out that natural law could be the natural instinctive behavior of
all God’s creatures. It could be the rules and norms of behavior that
governed primitive human beings before human societies established their
own particular laws. It could be the common sense of justice and equity that
one could find in all human laws. They also argued that human reason might
be a source of knowledge about the norms of natural law. It could be divine
law. It could be the Ius gentium.
The jurists discussed all these possible types of natural law and did not,
at first, give primacy of place to one. They distinguished between a natural
law that was established by nature and one that was established by the natural
order of the world. If nature can be said to create natural law, some jurists
concluded, then “nature is God” (natura, id est Deus). They did
not embrace a juristic pantheism but simply acknowledged that the word
“nature” in this sense could be used for the creator. The jurists
who commented on Gratian’s Decretum developed the most elaborate analysis
of natural law. The most important of the twelfth-century jurists, Huguccio
(ca. 1190), located the origin of natural law in human beings. Natural law
is reason, and that reason is a natural power of the soul (naturalis vis
animi) that permits them to distinguish good from evil. This reason is called
“law”(ius) because it commands and “law” (lex) because
it binds. Huguccio also summed up twelfth-century juristic opinion on the
force of natural law in human affairs. Natural law, he observed, consisted
of three levels of authority: commands, prohibitions, and indications or
declarations (demonstrationes). An example of a command was the precept to
“love your Lord God.” A prohibition of natural law may be taken
from the Ten Commandments, “Thou shalt not steal.” The third level
of natural law leads human beings to choose what is licit and good over what
is bad and evil. For example, in Gratian’s excerpt from Isidore of Seville
liberty is a state that should be granted to all human beings. Huggucio noted,
however, that all men are not free. Natural law leads men to liberty but
does not command it. Huguccio explained that although liberty has its roots
in natural law, God introduced slavery into the world because of human sins.
Although medieval thinkers had to confront Isidore’s elegant and stirring
maxim that expressed the basic norm of human freedom (una libertas omnium)
constantly, they could not overturn the institution of slavery that was endemic
in their world or undermine the rights of slave owners.
Medieval ideas about natural law were transmitted to the modern world primarily
through the vehicle of theology, especially the theology of St. Thomas Aquinas
(ca. 1225-1274). Thomas treated natural law comprehensively in his Summa
theologica in Book One, part two, questions 91 and 94. His conclusions drew
heavily on the thought of the jurists. Natural law has its origins in human
nature. This nature is the same in all human beings. Reason is the foundation
upon which all natural law is based. The primary goal of natural law is to
direct human beings toward the good. Men follow the dictates of natural law
in three ways: following the order that exists in nature, obeying what nature
has taught all animals, and, finally, pursuing the inclinations and tendencies
of human reason. When Thomas asked the question “Can natural law be
changed? (Summa theologica I-II q.94 a.5), he augmented the thought of the
jurists when he explained why some elements of natural law are immutable
and some are not. Natural law consisted of first principles that cannot be
changed and secondary principles that can be. Thomas explained how slavery
could be justified slavery by noting that it did not arise from nature but
from human reason for the benefit of human life.
Natural law became an integral part of medieval legal and theological thought.
In private law the jurists used natural law in creative ways to justify and
regulate particular legal institutions. Twelfth- and thirteenth-century jurists
of the Ius commune argued that property rights were protected by natural
law because when God forbade stealing, he sanctioned private property. Since
natural law protected private property, they concluded that even the emperor,
king or prince could not deprive a person of their property except for just
and necessary reasons. By the end of the twelfth century, the jurists included
contractual rights under the provisions of natural law. Consequently, they
even concluded that the emperor was bound by the contracts that he might
make with his subjects. The prince was not exempt from the precepts of natural
law. In the fourteenth century the jurists argued that the norms that governed
judicial procedure were also derived from natural law. Consequently every
person had an absolute right to be summoned, present witnesses, and have
a public trial. In an ingenious use of the story of God’s condemnation
of Adam and Eve in Genesis 3.9-12, the jurists decided that God had established
the norms of procedure when he conducted the first trial in the Garden of
Eden. By the end of the Middle Ages the Spanish theologian and jurist Francisco
de Vitoria (1492-1546) put forward the remarkable argument that the right
of the majority of people to render their consent in political matters was
also a norm of natural law.
In this short and far from complete catalogue of rights that theologians
and jurists grounded in the norms of natural law, an important point must
be emphasized. In some cases, like the norms of procedure, they found
justifications for their arguments in sacred scripture. In others, like the
inviolability of contracts, they could discover no precedents in sacred
scripture. Instead they relied on norms that had evolved in the Ius commune.
These norms conformed to reason, reason so compelling that they expressed
eternal truths, Huguccio’s and Aquinas’ “the reason of natural
law.”
By the end of the Middle Ages jurists and theologians had reached general
agreement about the structure and content of natural law. Gradually these
ideas about natural law migrated from the Ius commune into the customary,
local legal systems of Europe, and jurists incorporated natural law into
their discussions of local customary law. The thirteenth-century commentary
on English law that circulated under the name of “Bracton” borrowed
word for word the definitions of natural law from the jurists of the Ius
commune. Bracton’s discussion of natural law did not bear fruit in English
legal thought until the fifteenth and sixteenth century, but the seeds of
a natural law tradition in the common law were planted early.
The Iberian legal compilation, Las siete partitas, published during the reign
of Alfonso X the Wise (1221-1284), devoted the second title of book one to
natural law and the Ius gentium. This summary of natural law and its handmaiden,
the Ius gentium, also reflected the thought of the jurists. Natural law governs
all men and animals. Its precepts regulate the institutions of marriage and
the raising of children. The Ius gentium is law that is common for all men
but not animals. Its two fundamental principles are the rights of property
and self-defense. These two laws, the compilers stated, inform all the ordinances
that deal with those issues in this law book. Gregorio López de Tovar
(ca. 1496-1560) wrote an extensive commentary on Las siete partidas in the
sixteenth century. He emphasized that Aquinas’ natural reason was
fundamental for knowing and understanding the contents of natural law.
“Natural reason ‘inclines’ human beings to marry.” Marriage
is, therefore, founded on natural law. Even the natives in the new world
have a true marriage because natural reason instigates them to form this
bond. By the end of the Middle Ages the support, education, and inheritance
of children were generally considered to be precepts of natural law, and
López made the point that a child’s right of inheritance could
not be taken away by contract or custom. Spanish thinkers in the sixteenth
and seventeenth centuries made significant contributions to the development
of natural law thought.
Medieval natural law provided the basis of all discussions of natural law
in early modern juristic and philosophical thought. When Thomas Jefferson
wrote in the Declaration of Independence that “We hold these truths
to be self-evident, that all men are created equal, that they are endowed
by their Creator with certain unalienable rights, that among these are life,
liberty, and the pursuit of happiness,” the ultimate origins of his
ideas lay in medieval juristic and theological thought.
Bibliography
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Kenneth Pennington
The Catholic University of America
Washington, D.C.