Editing Parmenides (section)

== Legacy and study ==
[[File:Sanzio 01 Parmenides.jpg|thumb|Parmenides. Detail of ''[[The School of Athens]]'' by [[Rafael Sanzio|Raphael]].]]
As the first of the [[Eleatics]], Parmenides is generally credited with being the philosopher who first defined ontology as a separate discipline distinct from theology.{{sfn|Palmer|2020}} Parmenides was the first Western philosopher to consider the nature of existence itself,{{Sfn|Vamvacas|2009|p=138}} <!---- if heraclitus predates him, which is generally considered likely this part is not true "and the first to make a distinction between what exists and what seems to exist.{{Sfn|Vamvacas|2009|p=143}}"---> While previous philosophers like the Milesians developed theories of how things physically originated, Parmenides considered [[ontology]], or how things are, solely as an idea without reference to a physical basis.{{Sfn|Vamvacas|2009|p=136}} He likely rejected the theories of the Milesian school, which described the world as being derived from specific elements, as Parmenides rejected that Being was derived from anything.{{Sfn|Grondin|2012|p=6}}

Though his ideas preceded and influenced [[metaphysics]], modern philosophers do not consider Parmenides to have studied metaphysics himself, as Being is not a distinct entity from the physical world. Some exceptions exist, such as [[Pierre Aubenque]], who described Parmenides' work as "the birth certificate of Western metaphysics".{{Sfn|Grondin|2012|p=14}} Parmenides has been seen as the first Western philosopher to invoke what are now considered [[Law of thought|the basic principles of logic]]. His concepts of Being and Nonbeing are defined by the [[law of noncontradiction]]; since Being ''is'', it cannot ''not be'', and since Nonbeing ''is not'', it cannot ''be''. The [[law of excluded middle]] prevents the existence of something that neither ''is'' nor ''is not''.{{Sfn|Vamvacas|2009|p=139}} The [[principle of sufficient reason]] indicates that Being must ''be'' if it can be thought about, as a thought is something rather than nothing. Parmenides' conclusion is defined by the [[law of identity]], as Being is ''to be'' and Nonbeing is ''to not be''. By combining these logical processes, Parmenides proves a [[Tautology (logic)|tautology]] using a [[syllogism]].{{Sfn|Vamvacas|2009|p=140}}

Parmenides understood the Moon's illumination to be the reflection of sunlight off of its spherical surface. He is sometimes described as the first philosopher to describe the Earth as spherical and to identify the [[Phosphorus (morning star)|morning star]] and the [[Hesperus|evening star]] were both manifestations of a single object, Venus.{{Sfn|Vamvacas|2009|p=144}}

=== Ancient philosophy ===

==== Pre-Socratic philosophy ====
In modern interpretations, Parmenides is often seen as presenting a theory of unchanging "being" that spurred debate about the nature of change among subsequent natural philosophers in Presocratic philosophy.{{sfn|Palmer|2020|loc=§3.4}} However, there is no ancient testimony that supports this notion, and most interpreters of Parmenides in Antiquity appear to have read Parmenides as considering metaphysics and physics as two different aspects of the same reality.{{sfn|Palmer|2020|loc=§3.4}} Parmenides was a contemporary of [[Heraclitus]]. The two broached many of the same ideas, such as a world made of two competing opposites, reliability of the senses, and the nature of plurality—it is unclear if either influenced the other.{{Sfn|Vamvacas|2009|pp=157–158}}

Parmenides' philosophy formed the basis of the Eleatic school, which was continued by [[Melissus of Samos]] and [[Zeno of Elea]].  Melissus built on Parmenides' ideas, proposing a continuous eternal Being instead of a constant existence of the present. Zeno created ''[[reductio ad absurdum]]'' arguments to defend Parmenides' ideas against their critics.{{Sfn|Vamvacas|2009|p=150}}

In his work ''On Non-Being'', [[Gorgias]] includes both Parmenides and Melissus as philosophers who held that reality is one.{{sfn|Palmer|2020|loc=§3.4}} The pluralist theories of [[Empedocles]] and Anaxagoras and the atomists [[Leucippus]] and [[Democritus]] have also been seen as a potential response to Parmenides's arguments and conclusions.{{sfn|Sedley|1998}}

===Plato===
Along with [[Socrates]] and the [[Pythagoreans]], Parmenides was one of the greatest influences on Plato.{{sfn|Palmer|2020|loc=§3.4}}

In different places, Aristotle attributes the same epistemological position to Parmenides<ref>De Caelo 3.1</ref> that he does to Plato,<ref>Metaphysics 13.4</ref> that true knowledge must be grounded in an entity that is not subject to change.{{sfn|Palmer|2020|loc=§3.4}} This position is also endorsed by Plato himself at the end of the 5th book of the Republic.{{sfn|Palmer|2020|loc=§3.4}} For Plato, these are the forms from his own [[Theory of Forms]].{{sfn| Palmer| 2020| loc=§3.4}} In his own ''Parmenides'', Plato presents a fictional dialogue between Socrates and Parmenides where Parmenides himself also endorses this doctrine, that knowledge must be built on something unchanging.{{sfn| Palmer| 2020| loc=§3.4}}

Plato's understanding of Parmenides is further demonstrated by the second hypothesis in his ''Parmenides''<ref>Plato, Parmenides, 142b</ref> There, the One is shown to have different properties that parallel those laid about by Parmenides himself in Fragment 8: that the One is: in itself, the same as itself, at rest, like itself, and in contact with itself, both "in virtue of its own nature" and "in relation to itself."{{sfn| Palmer| 2020| loc=§3.4}} Plato then has Parmenides show that and that the One is ''not'' those same set of attributes, but only "contrary to its own nature" and "not in relation to itself," which parallels Parmenides own division of what is and what appears to be, that the "Way of Truth" corresponds to his own intelligible realm of forms, while the "Way of Opinion" corresponds to the sensible realm of matter.{{sfn| Palmer| 2020| loc=§3.4}} These two aspects of reality are also paralleled in Plato's ''Timaeus'' in the descriptions of the universe as a living creature perceived by reason and a cosmos modeled after it that is perceived by the senses.{{sfn| Palmer| 2020| loc=§3.4}} In the ''[[Sophist (dialogue)|the Sophist]]'', Plato gives a [[doxography]] of the Eleatics beginning not with Parmenides but with [[Xenophanes]], another pre-Socratic philosopher after whom Parmenides followed after, who believed true knowledge was only possible for the gods and that all else was opinion, which provides further support to the idea that Plato saw the monism of Parmenides as not eliminating the possibility of statements about the "Way of Opinion."

==== Aristotle ====
Aristotle, in his ''Physics'',<ref>Physics 1.8, 191a</ref> makes reference to unnamed philosophers who reject substantial change because they hold the view that no entity or substance comes into being, which superfically appears to resemble Parmenides own doctrine.{{sfn|Palmer|2020|loc=§3.4}} However, he cannot be referring to Parmenides here, because in other places<ref>Aristotle, On the Heavens 3.1 298b; Metaphysics 1.5 986b; Physics 1.2 184ab</ref> he distinguishes between Parmenides' account of "first philosophy" which is not subject to change, and Parmenides' account of natural philosophy, in which he admits the possibility of substantial change.{{sfn|Palmer|2020|loc=§3.4}} When Aristotle introduces Parmenides own doctrines in the ''Physics'',<ref>Physics 1.2-1.3</ref> alongside those of another Eleatic philosopher, [[Melissus of Samos]], he distinguishes between the more strict monism of Melissus, which held that there can only be one substance that exists, and Parmenides' more permissive monism, which considered everything that exists to be substance in virtue of the fact that it exists, but allowed for different substances to exist.{{sfn|Palmer|2020|loc=§3.4}}

==== Hellenistic and Roman philosophy ====
Some Ancient philosophers did view Parmenides as a strict monist like Melissus, though they represented a minority opinion.{{sfn|Palmer|2020|loc=§3.4}} Writing in the late 1st century CE, the [[Middle Platonist]] philosopher [[Plutarch]], in his treatise ''Against Colotes'' attributes this position to [[Colotes]], an [[Epicureanism|Epicurean]] philosopher from the Hellenistic period.{{sfn|Palmer|2020|loc=§3.4}} Plutarch, who like many Platonists saw Parmenides as a forerunner of Plato,{{sfn|Palmer|2020|loc=§3.4}} criticizes Colotes for misrepresenting Parmenides' position, stating that Parmenides distinction between what truly is and what things appear to be according to the senses should not be seen as a rejection of the latter, because, as Plutarch argues, one could not do that without rejecting the existence of the senses themselves.{{sfn|Palmer|2020|loc=§3.4}}

[[Eusebius of Caesarea]], quoting [[Aristocles of Messene]], says that Parmenides was part of a line of skeptical philosophy that culminated in [[Pyrrhonism]].<ref>[[Eusebius]], ''[[Praeparatio Evangelica]]'' [https://www.tertullian.org/fathers/eusebius_pe_14_book14.htm Book XIV], Chapter XVII</ref>{{primary source inline|date=May 2025}}

For Simplicus, a [[Neoplatonist]] philosopher writing in the 6th century, who preserves almost the entirety of our extant fragments of the treatise, the two accounts describes by the goddess in Parmenides poem correspond to two different levels of reality: the intelligible and eternal realm of forms, and the constantly changing sensible world.<ref>Simplicius, Commentary on Aristole's On the Heavens</ref>{{sfn|Palmer|2020|loc=§3.4}}

=== Modern era ===
The philosophy of [[Martin Heidegger]] revisited the concept of a Parmenidean eternal Being.{{Sfn|Grondin|2012|pp=10, 12}}{{Sfn|Vamvacas|2009|p=164}} He described Parmenides as the first to create a unified concept of Being and Nonbeing.{{Sfn|Vamvacas|2009|p=146}}

In ''On Nature'', Parmenides describes the truth as the path of ''that is''. The philologist [[Hermann Fränkel]] identified this use of an [[impersonal verb]] as an atypical grammatical construction in Ancient Greek. It is understood to refer to the concept of Being, described through [[postposition]].{{Sfn|Grondin|2012|p=10}} The goddess's description of Being is effectively the affirmation of its existence. Aubenque commented that this is "the thesis of Being itself".{{Sfn|Grondin|2012|p=11}} Ernst Hoffman proposed that Being, discourse, and thought were all the same thing.{{Sfn|Grondin|2012|p=13}}

[[Friedrich Nietzsche]] suggested that Parmenides believed his cosmology, even though he understood that it was only part of the seeming world. [[Karl Popper]] said that it was necessary for Parmenides to disprove his own cosmology to prove that the seeming world was not true. He likened this to modern physics, in which theories of physics do not necessarily correspond to what appears to be true.{{Sfn|Vamvacas|2009|p=145}}

The question of whether time and space are continuous or discrete is prominent in [[modern physics]], where several mathematicians and physicists propose Parmenidean models. [[Albert Einstein]] developed a single model of [[spacetime]] to explain the universe. [[Hermann Weyl]] argued that time exists only subjectively. [[Karl Popper]] further described the ideas of [[Ludwig Boltzmann]], [[Kurt Gödel]], [[Hermann Minkowski]], and [[Erwin Schrödinger]] as reminiscent of Parmenides. The [[Wheeler–DeWitt equation]] suggests that time does not exist as its own distinct entity.{{Sfn|Vamvacas|2009|p=163}}

Among the historians of philosophy and philologists: [[William Keith Chambers Guthrie]] observes that the figure of Parmenides is a fundamental milestone that divides the course of [[Pre-Socratic philosophy]] in two, because it stopped the inquiry into the origin and constitution of the universe and reoriented the course of archaic thought.<ref name = "guth15"/>  Coxon argues that Parmenides was the first genuine philosopher of the Greek world, the founder of European philosophy, and the first proper metaphysician, unlike the other pre-Socratics who discovered the principles of what is now known as science. said.<ref>Coxon, "The Philosophy of Parmenides," p. 144.</ref>