The debate over climate change, both from natural causes and human activity, is not new. Although the Baron C.-L. de Montesquieu is undoubtedly the best known Enlightenment thinker on the topic of climatic determinism, others, notably the Abbé Du Bos, David Hume, and Thomas Jefferson, observed that climatic changes exerted a direct influence on individuals and society and that human agency was directly involved in changing the climate. Climate—from the Greek term klima, meaning slope or inclination—was originally thought to depend only on the height of the Sun above the horizon, a function of the latitude. A second tradition, traceable to Aristotle, linked the quality of the air (and thus the climate) to the vapors and exhalations of a country. The Hippocratic tradition further linked climate to health and national character. As late as 1779, the Encyclopdédie of Denis Diderot and Jean le Rond D’Alembert defined “climat” geographically, as a “portion or zone of the surface of the Earth, enclosed within two circles parallel to the equator,” in which the longest day of the year differs in length on its northern and southern boundaries by some quantity of time, for example one-half hour. The article goes on to mention Montesquieu’s position on “l’influence du climat sur les mœurs, le charactère, et les loix des peuples.” The second definition of climate provided by the Encyclopdédie was medical, identified primarily as the temperature of a region and explicated through its effects on the health and well-being of the inhabitants. The idea that climate influenced culture was derived in part from the writings of ancient and medieval philosophers, geographers, and historians, including the works of Hippocrates, Albertus Magnus, and Jean Bodin. With no established science of climatology, Enlightenment thinkers apprehended climate and its changes primarily in a literary way. They compared the ancient writings to recent weather conditions, linked the rise and fall of creative historical eras to changes in climate, and promoted a brand of climatic determinism based on geographic location and the quality of the air.