The idea of elemental air grew out of the same classical framework as elemental water. Empedocles’ fifth-century-BCE scheme used four enduring roots: earth, water, air, and fire. Aristotle then systematized them within a physics of matter and change. In On Generation and Corruption, air is paired with the qualities hot and moist and treated as one of the primary bodies involved in the transformations of matter.
This framework survived because it did far more than provide a list of four substances. Aristotelian natural philosophy offered linked explanations for terrestrial matter, motion, weather, celestial structure, and living things. When Aristotle’s natural works became part of medieval and Renaissance university curricula, generations of scholars encountered “air” as a fundamental category within a coherent physical system.
The category began to fragment in the early modern period. Joseph Black distinguished “fixed air” (carbon dioxide); Henry Cavendish investigated inflammable air (hydrogen); Joseph Priestley isolated several different “airs,” including what Lavoisier later named oxygen. Lavoisier’s reinterpretation of combustion and respiration helped turn these proliferating airs into chemically distinct gases.
Modern air therefore looks almost like the reverse of the classical picture: what seems to the senses like one uniform substance is actually a mixture dominated by nitrogen and oxygen, with argon, carbon dioxide, water vapor, and trace gases.