In order to understand what guidance natural law gives us about war and peace in our time, it is first necessary to have some understanding of what ‘natural law’ is.

The way of an eagle in the air; the way of a serpent upon a rock; the way of a ship in the midst of the sea; and the way of a man with a maid.

—Proverbs 30:19

In order to understand what guidance natural law gives us about war and peace in our time, it is first necessary to have some understanding of what “natural law” is. Far from being a hazy concept peculiar to some philosophers, natural law is quite simply how the world works. It is reality.

Our very civilization is based on understanding that nature and man exist and behave according to laws that our minds can grasp by observation and study. Only recently has it become customary to distinguish between facts and values—that is, between what is and what we want.

Formerly, the fundamental distinction was between truth (reality) and opinions (the thoughts we winnow to understand reality). The people who built the United States believed that attention to the laws of nature and of nature’s God was the key to thriving because they knew that ignoring or flouting reality does not turn out well.

Physics and chemistry remind us that natural law is inflexible and self-enforcing. You may “identify” as a bird, eat bird food, and wear feathers. But if you jump off a cliff chirping and flopping those feathers, Mother Nature’s laws regarding mass and motion will punish you. Nor will she let you make salt out of two sodium atoms, regardless of your commitment.

Plants are just as subject to laws. Regardless of anybody’s opinion, apples, oranges, and avocados require different conditions to thrive. That is why judgments about farming have to be right by nature, or else.

Not so long ago, the Soviet government, following a scientific consensus that acquired characteristics are inherited, wasted millions of tons of seeds trying to modify wheat to grow in Siberia. In America today, scientific consensus has it that the globe is warming, and yet citrus growers are moving their operations southward because the trees don’t share that consensus. Mother Nature does not care what anybody thinks.

Wild animals are, as the saying goes, “hardwired” to survive and thrive, moving and reproducing to take optimal advantage of weather and food sources. They can’t help doing the right things for themselves. So far as we know, human beings are the only part of creation capable of doing the wrong things for themselves.

But that freedom doesn’t affect nature’s peculiar requirements for human beings to survive and thrive. Human survival, like that of other mammals, starts with food and community. But the happiness of these creatures, who are more than animals but less than gods, requires more.

This is the opening of a Claremont Review of Books article unlocked for Federalist readers. To keep reading, please visit their website.