Answer the following question given this paragraph: 

The idea of elements is not new. It dates back about 2500 years to ancient Greece. The ancient Greek philosopher Aristotle thought that all matter consists of just four elements. He identified the elements as earth, air, water, and fire. He thought that different kinds of matter contain only these four elements but in different combinations.


Q: The ancient greek philosopher aristotle thought that all matter consists of just four what, which he identified as earth, air, water, and fire?


A:
elements