The philosopher who believes that the universe is made only of matter in the void is Democritus. He was a Greek philosopher who lived in the 5th century BCE and is known for his atomic theory of the universe.
According to Democritus, matter is defined as the fundamental building block of the universe, which cannot be further subdivided. He believed that everything in the universe, including the human body and soul, is made up of atoms that are constantly moving and interacting with one another. These atoms are eternal and indestructible, and they exist in an infinite void.
The void, or "empty space," according to Democritus, is another fundamental concept in his philosophy. He argued that the void is not nothingness but rather a space that is free of matter. This void allows for the movement of atoms within the universe, and without it, there would be no observable movement or change.
For Democritus, the universe was a vast and infinite space that is filled with matter and separated by an infinite void. His atomic theory of the universe was revolutionary at the time, and it laid the groundwork for modern atomic theory that is still used in science today.