Written in the Heart of Man

Sophocles' character Antigone speaks of "the unwritten laws of heaven" that no man can change or override. She is referring to the eternal law. Eternal law is God's plan for all creation "to run" with each being living according to it's nature. The natural law is simply eternal law in the heart of the human person. Since he has reason, a human being can know what is good and what is bad (evil). That's why it's called "natural law", because it's based on reason, which is the basis of human nature. No other visible creature on earth is able to reason. Thus, man's reason telling him to choose what is good and avoid what is evil has come to be called "the natural law." Indeed, this is the first principle of the natural law: Do good and avoid evil. "This first principle of natural law: 'Do good and avoid evil.' is known to anyone who has the use of reason at all." (Austin Fagothey, Right and Reason Rockford, IL: Tan Books and Publishers, 1959, p.179). "My dear Sam," every hobbit--I mean--every human being has at least some use of reason. That is what makes him human. From these principles, other basic principles immediately follow. They are so simple that everyone has them.

There are other common or general principles based on the first principle, following from it with immediate inference, or with mediate inference so simple and easy that no normal mature person can fail to make it. (Ibid., p. 179)

Austin Fagothey's book Right and Reason gives these examples:

"Preserve your own being."
"Care for your offspring."
"Adore God."
"Do not murder."
"Treat others with fairness."
"Be faithful to your friends." (page 179)

No human person wants to die or get sick. We naturally abhor such painful experiences. And who doesn't like a cute little baby! And when the baby is your own you definitely want him or her to continue to live; parents are willing to give their very lives for their children. Everyone feels a need to worship and if one doesn't find the true God, he makes up his own god or accepts the god of his peers--whichever one happens to be popular at the time. It's obvious that religion cannot be eradicated from the human race. Everyone wants to be treated fairly, and everyone--especially children--has a sense of fair play. Finally, no man can exist totally alone; everyone needs a friend. This is so deep in man. It is in all our great literature, our tales, our stories--from Day One.

Enkidu, whom I loved dearly,
who went with me through all hardships,
He has gone to the lot of mankind,
Day and night I have wept over him.
For burial I did not want to give him up, thinking:
"My friend will rise after all at my lamentations!"
From: Epic of Gilgamesh, Tablet X (Old Babylonian version), lines 2-11, in Heidel, Gilgamesh Epic, p. 69.