Anaxagoras believed in two types of existence which are the mind and matter. Matter makes up the part of the universe that is all physical. There is no such thing as the smallest particle because they keep on dividing nonstop. They are composed of all four elements fire, earth, water and air. These four elements are what make up the earth if they are combined, like earth and water will make mud. It is just like the objects of experience, the four element combine to form larger objects.
The mind is its own substance. The mind in not mixed with anything else it is pure. It is omnipresent, omnipotent and omniscient. It does not have any matter to it. The mind does not create the matter it rearranges it. The universe starts as an infinite mass. Then the mind makes up shapes to create a world. Finally it creates objects out of experience. The mind doesn’t act with a purpose it just acts.