The Eleatics, a pre-Socratic philosophical school founded by Parmenides in the early fifth century BC, originated in the ancient town of Elea in present-day southern Italy. This school's key members, including Zeno of Elea and Melissus of Samos, built on and challenged the metaphysical ideas of Xenophanes of Colophon, who some argue was the school's actual founder.
The Eleatics had a profound impact on Platonic metaphysics by questioning fundamental concepts, including the possibility of motion. Their approach rejected the veracity of sense experience as a way to attain knowledge. Instead, they prioritized logical standards of clarity and necessity as the true criteria of truth. They used sound premises and reductio ad absurdum, a method of disproving a theory by demonstrating that it leads to absurd or self-contradictory outcomes, as seen in Zeno's paradoxes.
Contrary to early physicalist philosophers who explained existence in terms of primary matter, and Heraclitus' theory of perpetual change, the Eleatics proposed a universal unity of being as the true explanation of things. They argued that this unity could not be comprehended through the senses due to their inherent inconsistencies. Instead, through thought alone, one could transcend these false sensory appearances and realize the fundamental truth that "All is One". The Eleatics also contended that creation was impossible, as being could not arise from non-being, pinpointing the often-ambiguous use of the verb 'to be' as a common source of error in understanding existence.
Despite the cessation of the Eleatic school with Melissus of Samos and the subsequent rejection of their conclusions by later Pre-Socratics and Aristotle, their arguments were influential and contributed to enhancing the standards of discourse and argument. Notable figures such as Gorgias, a Sophist, employed Eleatic-style arguments, and Plato acknowledged them in his dialogues. The methodologies and principles of the Eleatics greatly influenced the later philosophy of the ancient period.