Empedocles an early Greek philosopher agreed with Parmenides, an influential Greek philosopher, that what exists is eternal and unchanging. But Empedocles explained the experience of change by rejecting Parmenides' notion that the universe consists of one basic substance. Empedocles became the first philosopher to argue that what exists can be reduced to four elements--air, earth, fire, and water. He said that all other substances result from temporary combinations of these elements. The elements are eternal and unchanging, but their combining and separating appear as change.
Empedocles said that "a force called love " causes the elements to come together as compounds, and that a force called strife causes the compounds to break up. He believed that the universe undergoes a continuous cycle from complete unification of the elements under the domination of love to complete separation of the elements under strife. The world we live in occurs between these two extreme states.
