, PLEASE USE THIS DOCUMENT AS A GUIDE ONLY
QUESTION 1
1. Identify the legal philosophical approach that Martin Luther King Jr. advocates in his letter
and explain how this approach originated and developed.
King explicitly distinguishes between just and unjust laws, asserting that a just law is a “man‑made
code that squares with the moral law or the law of God,” while an unjust law is “out of harmony with
the moral law.”¹ He supports this by citing St. Thomas Aquinas’s position that “an unjust law is a
human law that is not rooted in eternal law and natural law.”² This reflects the core natural law
proposition that a positive (human‑made) law derives its validity from its conformity to a higher,
moral standard; a law that violates that standard is not truly law and carries no moral obligation of
obedience.
The natural law approach originated in ancient Greek philosophy, particularly in Aristotle’s idea of a
“natural justice” that is universal and not merely a matter of convention. It was developed
systematically by Stoic thinkers, who emphasized a rational, universal law governing all humanity.
The tradition was then integrated into Western legal thought by Roman jurists and, most influentially
for King, by medieval theologians. St. Augustine (354–430 CE) formulated the classic maxim “an
unjust law is no law at all,” which King directly quotes.³ St. Thomas Aquinas (1225–1274 CE) then
refined the doctrine by distinguishing four types of law: eternal (God’s reason), natural (the rational
creature’s participation in eternal law), divine (revealed law), and human (positive law). For Aquinas,
a human law that contradicts natural law is a “perversion of law” and does not bind in conscience.⁴
During the Enlightenment, natural law theory was secularised by thinkers such as Hugo Grotius,
John Locke, and Samuel von Pufendorf, who grounded it in reason and social contract rather than
theology. Locke’s ideas heavily influenced the American Declaration of Independence and the
constitutional tradition. In the twentieth century, natural law reasoning was revived in moral and
legal philosophy by figures such as Lon L. Fuller, John Finnis, and, in the context of civil rights,
Martin Luther King Jr., who blended the theological natural law of Augustine and Aquinas with the
American constitutional promise of equal dignity. King’s letter thus stands in a tradition that runs
from Aristotle through Aquinas and Locke to modern struggles against positive laws that enforce
racial segregation.
¹ Martin Luther King Jr., “Letter from Birmingham Jail,” 16 April 1963, in Why We Can’t Wait (New York: Harper & Row, 1964),
reprinted at African Studies Center, University of Pennsylvania, https://www.africa.upenn.edu/Articles_Gen/Letter_Birmingham.html
(accessed 27 March 2026).
² King, “Letter from Birmingham Jail.”
³ King, “Letter from Birmingham Jail,” citing St. Augustine.
⁴ Thomas Aquinas, Summa Theologica, I–II, q. 95, a. 2 (on human law and its relation to natural law).
QUESTION 1
1. Identify the legal philosophical approach that Martin Luther King Jr. advocates in his letter
and explain how this approach originated and developed.
King explicitly distinguishes between just and unjust laws, asserting that a just law is a “man‑made
code that squares with the moral law or the law of God,” while an unjust law is “out of harmony with
the moral law.”¹ He supports this by citing St. Thomas Aquinas’s position that “an unjust law is a
human law that is not rooted in eternal law and natural law.”² This reflects the core natural law
proposition that a positive (human‑made) law derives its validity from its conformity to a higher,
moral standard; a law that violates that standard is not truly law and carries no moral obligation of
obedience.
The natural law approach originated in ancient Greek philosophy, particularly in Aristotle’s idea of a
“natural justice” that is universal and not merely a matter of convention. It was developed
systematically by Stoic thinkers, who emphasized a rational, universal law governing all humanity.
The tradition was then integrated into Western legal thought by Roman jurists and, most influentially
for King, by medieval theologians. St. Augustine (354–430 CE) formulated the classic maxim “an
unjust law is no law at all,” which King directly quotes.³ St. Thomas Aquinas (1225–1274 CE) then
refined the doctrine by distinguishing four types of law: eternal (God’s reason), natural (the rational
creature’s participation in eternal law), divine (revealed law), and human (positive law). For Aquinas,
a human law that contradicts natural law is a “perversion of law” and does not bind in conscience.⁴
During the Enlightenment, natural law theory was secularised by thinkers such as Hugo Grotius,
John Locke, and Samuel von Pufendorf, who grounded it in reason and social contract rather than
theology. Locke’s ideas heavily influenced the American Declaration of Independence and the
constitutional tradition. In the twentieth century, natural law reasoning was revived in moral and
legal philosophy by figures such as Lon L. Fuller, John Finnis, and, in the context of civil rights,
Martin Luther King Jr., who blended the theological natural law of Augustine and Aquinas with the
American constitutional promise of equal dignity. King’s letter thus stands in a tradition that runs
from Aristotle through Aquinas and Locke to modern struggles against positive laws that enforce
racial segregation.
¹ Martin Luther King Jr., “Letter from Birmingham Jail,” 16 April 1963, in Why We Can’t Wait (New York: Harper & Row, 1964),
reprinted at African Studies Center, University of Pennsylvania, https://www.africa.upenn.edu/Articles_Gen/Letter_Birmingham.html
(accessed 27 March 2026).
² King, “Letter from Birmingham Jail.”
³ King, “Letter from Birmingham Jail,” citing St. Augustine.
⁴ Thomas Aquinas, Summa Theologica, I–II, q. 95, a. 2 (on human law and its relation to natural law).
