What was a major competing theory in ancient greece for the atomic theory of matter?

In ancient Greece, the major competing theory for the atomic theory of matter was the "Four Element Theory," which was proposed by Empedocles. According to this theory, all matter was composed of four fundamental elements: earth, water, air, and fire. Empedocles believed that different combinations of these elements resulted in the variety of substances observed in the world.

This theory contrasted with the atomic theory proposed by Leucippus and his student Democritus. According to the atomic theory, matter was composed of indivisible and indestructible particles called "atoms." These atoms were believed to be in constant motion and could combine to form different substances.

While the Four Element Theory dominated early Greek philosophy, the atomic theory gained prominence later, especially during the time of Leucippus and Democritus in the 5th century BCE. However, both theories persisted in various forms, and the debate between the two continued for centuries. It wasn't until the development of modern atomic theory in the 19th century that the idea of atoms as fundamental particles gained widespread acceptance.