In 1748, the French philosopher Montesquieu published The Spirit of the Laws, a survey of political systems that argued for the separation of powers and citizens’ rights to due process. It was quickly translated into multiple languages, and Montesquieu’s ideas about liberty had a strong influence on the framers of the American Constitution.
In the book, after discussing taxes and before considering slavery, Montesquieu set out a theory that climate differences help to shape human societies. Based on pre-modern medicine, Montesquieu believed that cold air constricts the body’s “fibers” and increases blood flow, while warm air relaxes those same fibers. “People are therefore more vigorous in cold climates,” he wrote. “This superiority of strength must produce various effects; for instance, a greater boldness, that is, more courage; a greater sense of superiority... .”