Which philosopher believed the universe is one single, perfect sphere?

Parmenides is recognized for his philosophical stance that emphasizes the idea of a unified and unchanging reality. He proposed that change and plurality are mere illusions and that true existence is eternal and unalterable. By arguing that the universe is a singular, perfect sphere, he is asserting that all that truly exists is one, consistent entity. This conceptualization reflects his belief that the underlying essence of reality is uniform and indivisible, contrasting with views that embrace change and multiplicity.

Heraclitus, on the other hand, is known for his belief that everything is in flux and that change is the fundamental nature of the universe. Zeno is recognized for his paradoxes, which challenge the concepts of motion and plurality, but do not specifically focus on the idea of the universe as a perfect sphere. Socrates, primarily known for his contributions to ethics and epistemology based on dialogue and questioning, did not engage in cosmological theories in the manner that Parmenides did. Thus, Parmenides stands out as the philosopher who articulated the notion of the universe as a singular, perfect sphere, emphasizing the idea of unity over diversity.