LEGAL POSITIVISM vs. NATURAL LAW THEORY
There are two “natural law” theories about two different things: i) a natural law theory of
morality, or what’s right and wrong, and ii) a natural law theory of positive law, or what’s
legal and illegal. The two theories are independent of each other: it’s perfectly consistent
to accept one but reject the other. Legal positivism claims that ii) is false. Legal positivism
and the natural law theory of positive law are rival views about what is law and what is its
relation to justice/morality.
Natural Law Theory of Morality
i) Even things which are not man-made (e.g. plants, rocks, planets, and people)
have purposes or functions, and the “good” for any thing is the realization of its purpose or
function.
ii) The good for us human beings is happiness, the living of a flourishing life.
Happiness or flourishing consists in the fulfillment of our distinctive nature, what we “by
nature” do best. That involves the development and exercise of our capacities for
rationality, abstract knowledge, deliberative choice, imagination, friendship, social
cooperation based on a sense of justice, etc. The moral virtues (e.g. courage, justice,
benevolence, temperance) are character traits that help us fulfill our true nature. The life of
the heroin addict or of the carnal hedonist is not a good one, because it is inconsistent with
our natural function.
iii) Natural law is the set of truths about morality and justice; they are rules that we
must follow in order to lead a good or flourishing life. We can know what these principles
are by means of unaided human reason. [The natural law theory of morality rejects ethical
subjectivism (“right and wrong are all a matter of opinion”) and affirms ethical objectivism
(“some moral opinions are more valid, reasonable, or likely to be true than others”)].
Immoral acts violate natural law. Hence, immoral behavior is “unnatural” (in the sense of
“contrary to our function,” not “nowhere to be found in the natural world”), whereas
virtuous behavior is “natural.” For example, lying is unnatural, Aquinas holds, because the
function of speech is to communicate to others what is in our minds. When we use words
to mislead others, we are using them contrary to their proper function.
Natural Law Theory of Law
Legal systems have a function—to secure justice. Grossly unjust laws (e.g. “White
people may own Black people as slaves,” “women may not own property or vote”) are not
really laws at all, but a perversion of law or mere violence. As St. Augustine put it, lex
injustia non est lex. Aquinas’s way of stating this point: positive law has as its purpose the
common good of the community. Any positive law which conflicts/is inconsistent with
either natural law or divine law is not really law at all. Hence, not only is there no moral
obligation to obey it, but there is no legal obligation to obey it, either. Augustine, Aquinas,
and Martin Luther King are supporters of this view.
Lon Fuller argued there is some necessary overlap between legality and justice, because it’s
impossible to have a legal system without fidelity to the rule of law and formal justice.
(Fuller would probably have cited Iraq under Saddam Hussein as a good example of a
society that violated the rule of law so much that it really had no genuine legal system at
, all). But Fuller does not go as far as Augustine or Aquinas, because he admits that a
society can have a genuine legal system that satisfies the demands of formal justice (“like
cases must be treated alike”) yet still have particular laws that are unjust. In such a society,
judges are independent of the other branches of government and decide cases on their
merits, the society honors the principles “no punishment without a crime” and “no crime
without a pre-existing, public law,” the accused receives a fair trial with due process of law,
etc. But still, some of the laws that are consistently and fairly enforced are unjust (e.g.
“women may not own property or vote”).
Ronald Dworkin, whom will talk about more later, defends a view of legal interpretation
(by judges) that he claims is in the tradition of the natural law theory of positive law.
Dworkin argues it is proper for Supreme Court justices to interpret the Constitution in light
of the correct principles of justice that our country tries to honor.
Legal Positivism—
Whether a certain rule is a law, creating legal obligations to comply with it, all
depends on its source. Valid laws are simply rules that come from certain people (kings,
city councils, etc.), in accordance with certain procedures, that the society enforces. A rule
can be a genuine, valid law even though it is grossly unjust. According to H.L.A. Hart, a
contemporary legal positivist, the essence of legal positivism is the “separation thesis.”
Separation thesis: having a legal right to do x doesn’t entail having a moral right to
do it, and vice versa; having a legal obligation to do something doesn’t entail
having a moral right to do it, and vice versa; having a legal justification to do
something doesn’t entail having a moral justification, and vice versa; etc.
In order to know what your legal rights are, you need to look at what laws your society has.
In order to know what your moral rights are, you need to figure out what is the true
morality. You might have legal rights that the true morality says you shouldn’t have (e.g.
the right to own slaves), and your society might deny you legal rights that the true morality
says you should have (e.g. the right to be free, to own one’s own body and labor power).
-- Some of the most influential defenders of legal positivism are the 19th century
philosophers John Austin and Jeremy Bentham, and the 20th century legal philosopher
H.L.A. Hart.
Some terminology from Aquinas and Austin
Aquinas distinguishes four types of law—human, divine, eternal, and natural—as follows:
Human law—“an ordinance of reason for the common good promulgated by him
who has the care of the community.”
Eternal law —God’s plan for all of creation.
Natural law—The part of eternal law that applies to human beings; it is God’s plan
for us. Natural law can be discerned by unaided human reason, and it consists in the
There are two “natural law” theories about two different things: i) a natural law theory of
morality, or what’s right and wrong, and ii) a natural law theory of positive law, or what’s
legal and illegal. The two theories are independent of each other: it’s perfectly consistent
to accept one but reject the other. Legal positivism claims that ii) is false. Legal positivism
and the natural law theory of positive law are rival views about what is law and what is its
relation to justice/morality.
Natural Law Theory of Morality
i) Even things which are not man-made (e.g. plants, rocks, planets, and people)
have purposes or functions, and the “good” for any thing is the realization of its purpose or
function.
ii) The good for us human beings is happiness, the living of a flourishing life.
Happiness or flourishing consists in the fulfillment of our distinctive nature, what we “by
nature” do best. That involves the development and exercise of our capacities for
rationality, abstract knowledge, deliberative choice, imagination, friendship, social
cooperation based on a sense of justice, etc. The moral virtues (e.g. courage, justice,
benevolence, temperance) are character traits that help us fulfill our true nature. The life of
the heroin addict or of the carnal hedonist is not a good one, because it is inconsistent with
our natural function.
iii) Natural law is the set of truths about morality and justice; they are rules that we
must follow in order to lead a good or flourishing life. We can know what these principles
are by means of unaided human reason. [The natural law theory of morality rejects ethical
subjectivism (“right and wrong are all a matter of opinion”) and affirms ethical objectivism
(“some moral opinions are more valid, reasonable, or likely to be true than others”)].
Immoral acts violate natural law. Hence, immoral behavior is “unnatural” (in the sense of
“contrary to our function,” not “nowhere to be found in the natural world”), whereas
virtuous behavior is “natural.” For example, lying is unnatural, Aquinas holds, because the
function of speech is to communicate to others what is in our minds. When we use words
to mislead others, we are using them contrary to their proper function.
Natural Law Theory of Law
Legal systems have a function—to secure justice. Grossly unjust laws (e.g. “White
people may own Black people as slaves,” “women may not own property or vote”) are not
really laws at all, but a perversion of law or mere violence. As St. Augustine put it, lex
injustia non est lex. Aquinas’s way of stating this point: positive law has as its purpose the
common good of the community. Any positive law which conflicts/is inconsistent with
either natural law or divine law is not really law at all. Hence, not only is there no moral
obligation to obey it, but there is no legal obligation to obey it, either. Augustine, Aquinas,
and Martin Luther King are supporters of this view.
Lon Fuller argued there is some necessary overlap between legality and justice, because it’s
impossible to have a legal system without fidelity to the rule of law and formal justice.
(Fuller would probably have cited Iraq under Saddam Hussein as a good example of a
society that violated the rule of law so much that it really had no genuine legal system at
, all). But Fuller does not go as far as Augustine or Aquinas, because he admits that a
society can have a genuine legal system that satisfies the demands of formal justice (“like
cases must be treated alike”) yet still have particular laws that are unjust. In such a society,
judges are independent of the other branches of government and decide cases on their
merits, the society honors the principles “no punishment without a crime” and “no crime
without a pre-existing, public law,” the accused receives a fair trial with due process of law,
etc. But still, some of the laws that are consistently and fairly enforced are unjust (e.g.
“women may not own property or vote”).
Ronald Dworkin, whom will talk about more later, defends a view of legal interpretation
(by judges) that he claims is in the tradition of the natural law theory of positive law.
Dworkin argues it is proper for Supreme Court justices to interpret the Constitution in light
of the correct principles of justice that our country tries to honor.
Legal Positivism—
Whether a certain rule is a law, creating legal obligations to comply with it, all
depends on its source. Valid laws are simply rules that come from certain people (kings,
city councils, etc.), in accordance with certain procedures, that the society enforces. A rule
can be a genuine, valid law even though it is grossly unjust. According to H.L.A. Hart, a
contemporary legal positivist, the essence of legal positivism is the “separation thesis.”
Separation thesis: having a legal right to do x doesn’t entail having a moral right to
do it, and vice versa; having a legal obligation to do something doesn’t entail
having a moral right to do it, and vice versa; having a legal justification to do
something doesn’t entail having a moral justification, and vice versa; etc.
In order to know what your legal rights are, you need to look at what laws your society has.
In order to know what your moral rights are, you need to figure out what is the true
morality. You might have legal rights that the true morality says you shouldn’t have (e.g.
the right to own slaves), and your society might deny you legal rights that the true morality
says you should have (e.g. the right to be free, to own one’s own body and labor power).
-- Some of the most influential defenders of legal positivism are the 19th century
philosophers John Austin and Jeremy Bentham, and the 20th century legal philosopher
H.L.A. Hart.
Some terminology from Aquinas and Austin
Aquinas distinguishes four types of law—human, divine, eternal, and natural—as follows:
Human law—“an ordinance of reason for the common good promulgated by him
who has the care of the community.”
Eternal law —God’s plan for all of creation.
Natural law—The part of eternal law that applies to human beings; it is God’s plan
for us. Natural law can be discerned by unaided human reason, and it consists in the
