Prodicus of Ceos (c. 465–415 B.C.E.) said that Empedocles’ four elements of earth, wind, fire, and water were divine (a doctrine that the playwright Aristophanes (c. 446–386) made fun of in The Birds). He also thought that whatever was necessary to human beings was considered holy, which was not a traditional view of religion in ancient Greece.

Prodicus argued that there is no absolute good, because what is good for one man is not necessarily good for another, a doctrine that supported relativism. In his discussions of language, Prodicus tried to show how no two words can have the same meaning. He also disagreed with Democratus (c. 460–371 B.C.E.), who had said that there could be different names for the same thing.