Aristotle’s Theory of Chemical Reaction and Chemical Substances

The dominance of atomic structure in modern chemistry has led to an emphasis of the atomic tradition which overshadows what the subject owes to the other traditions. But there are definite features of modern chemical theory which hark back to one or other of the anti-atomistic conceptions. Aristotle maintained that the appearance of genuinely new substances, with properties radically different from the original constituents’, could not be explained by the atomic theory. Some points of his critique of the atomists’ theory of mixing could still be applied to 19th century atomism, and call for some care in discerning what general ideas have actually been retained from the atomic tradition. He argued that compounds are genuinely homogeneous—i.e. every part of any quantity of a compound is of the same kind as the whole—which led him to maintain that the constituents are not actually, but merely potentially, present in a compound. The theory is not without difficulties of its own. The present paper reviews the way Aristotle motivated his own approach and pursues the idea of constituents being potentially present in a compound.