Editing History of logic (section)

====Heraclitus and Parmenides====
The writing of [[Heraclitus]] (c. 535 – c. 475 BC) was the first place where the word ''[[logos]]'' was given special attention in ancient Greek philosophy,<ref>F.E. Peters, ''Greek Philosophical Terms'', New York University Press, 1967.</ref> Heraclitus held that everything changes and all was fire and conflicting opposites, seemingly unified only by this ''Logos''. He is known for his obscure sayings.
{{blockquote|This ''logos'' holds always but humans always prove unable to understand it, both before hearing it and when they have first heard it. For though all things come to be in accordance with this ''logos'', humans are like the inexperienced when they experience such words and deeds as I set out, distinguishing each in accordance with its nature and saying how it is. But other people fail to notice what they do when awake, just as they forget what they do while asleep.|[[Diels-Kranz]]|22B1}}
[[File:Busto di Parmenide (cropped).jpg|thumb|160px|Parmenides has been called the discoverer of logic.]]

In contrast to Heraclitus, [[Parmenides]] held that all is one and nothing changes. He may have been a dissident Pythagorean, disagreeing that One (a number) produced the many.<ref>{{cite book |author-last=Cornford |author-first=Francis MacDonald |url=https://www.bard.edu/library/arendt/pdfs/Cornford-Parmenides.pdf |title=Plato and Parmenides: Parmenides' ''Way of Truth'' and Plato's ''Parmenides'' translated with an introduction and running commentary |publisher=Liberal Arts Press |date=1957 |orig-date=1939}}</ref> "X is not" must always be false or meaningless. What exists can in no way not exist. Our sense perceptions with its noticing of generation and destruction are in grievous error. Instead of sense perception, Parmenides advocated ''logos'' as the means to Truth. He has been called the discoverer of logic,<ref>{{cite book |title=Western Philosophy: an introduction |author=R. J. Hollingdale |date=1974 |page=73}}</ref><ref>{{cite book |author-last=Cornford |author-first=Francis MacDonald |url=https://www.wilbourhall.org/pdfs/From_religion_to_philosophy.pdf |title=From religion to philosophy: A study in the origins of western speculation |publisher=Longmans, Green and Co. |date=1912}}</ref>

{{blockquote|For this view, that That Which Is Not exists, can never predominate. You must debar your thought from this way of search, nor let ordinary experience in its variety force you along this way, (namely, that of allowing) the eye, sightless as it is, and the ear, full of sound, and the tongue, to rule; but (you must) judge by means of the Reason ([[Logos]]) the much-contested proof which is expounded by me.|B 7.1–8.2}}

[[Zeno of Elea]], a pupil of Parmenides, had the idea of a standard argument pattern found in the method of proof known as ''[[reductio ad absurdum]]''. This is the technique of drawing an obviously false (that is, "absurd") conclusion from an assumption, thus demonstrating that the assumption is false.<ref>Kneale p. 15</ref> Therefore, Zeno and his teacher are seen as the first to apply the art of logic.<ref>{{cite web |url=https://books.google.com/books?id=DPoqAAAAMAAJ&pg=PA170 |title=The Numismatic Circular |date=2 April 2018 |access-date=2 April 2018 |via=Google Books |last1=Son |first1=Spink }}</ref> Plato's dialogue [[Parmenides (dialogue)|Parmenides]] portrays Zeno as claiming to have written a book defending the [[monism]] of Parmenides by demonstrating the absurd consequence of assuming that there is plurality. Zeno famously used this method to develop his [[Zeno's Paradoxes|paradoxes]] in his arguments against motion. Such ''dialectic'' reasoning later became popular. The members of this school were called "dialecticians" (from a Greek word meaning "to discuss").