Melissus of Samos was a member of the ancient Eleatic school of philosophy alongside notable figures like Zeno and Parmenides, and served as the commander of the Samian fleet in the Samian War. His major contribution was a treatise providing systematic arguments in favor of Eleatic philosophy, arguing that reality is ungenerated, indestructible, indivisible, changeless, and motionless. Melissus diverged from Parmenides by asserting that reality is unlimited and infinite in all directions and is singular in existence.
Little is known about his life apart from his military career and his philosophical pursuits. He was allegedly a student of Parmenides and the teacher of Leucippus, but these claims are met with skepticism. His philosophical treatise, titled "On Nature," was written in prose instead of poetry, making it more accessible than the works of Parmenides. Melissus proposed that reality, or "The One," was eternal, arguing against the notion of a beginning or end and positing an eternal past and future. However, this claim was criticized for logical flaws.
Melissus also claimed that The One is unlimited, possibly referring to spatial infinity. However, the clarity of this argument is uncertain. He argued that The One is singular, based on the assumption of spatial and temporal infinity. Additionally, Melissus proposed that The One is qualitatively the same, can't undergo any change, and is motionless. His claim that The One is incorporeal, despite being extended and full, aimed to address potential problems in Parmenides' philosophy.
Melissus' treatise influenced atomism and was crucial for the presentation of Eleatic philosophy in the works of Plato and Aristotle. However, he was heavily criticized by Aristotle for his allegedly crude work and invalid arguments. Despite this, modern philosophers have credited Melissus for his clear arguments and contributions to Eleatic philosophy.