|The Heraclitus vs Parmenides debate, sparked around 480BC, revolved around the question of “being” (or personhood) and “void” (or vacuum), the latter explicable, via pure materialism, but inherently negating the validity of the former.|
Shown adjacent, is the section from Italian painter Raphael's 1510 depiction of the School in Athens, Greece, showing: Parmenides, representative of the immovable being view, Heraclitus, representative of the flux, fire, and eternal change view of nature, amid an unnamed woman, said to be representative of "love", who glares out of the scene, in a strikingly peculiar way, that draws one's attention.
Parmenides, of note, was head of the so-called Eleatic school, whose members included Melissus (500-440BC) and Zeno of Elea (495-430BC), the latter a said “pupil” of Leucippus (who, supposedly, conceived "atomic theory" in reaction to Parmenides' denial of the void), intellectual mentor of Epicurus, the school of which, in reaction Heraclitus' materialism philosophy, went on a full out "attack" (Ѻ) on Heraclitus, arguing that all that existed was some type of immovable “being”, and concordantly that “non-being” or void was impossible; the deeply entrenched debate finding prolonged discussion in the two-millennium long nature abhors a vacuum; which, via the experiments of Otto Guericke, resultantly worked to initiate the science of thermodynamics, and in turn quantum mechanics, via Max Planck, and, in turn, relativity, via Albert Einstein.
Originally, in circa 505BC, Greek philosopher Heraclitus (535-450BC) developed a “flux and fire” philosophy, according to which, in his view:
“The universe, that is the all, is made neither of gods nor men, but ever has been and ever will be an eternal living fire, kindling and extinguishing in destined measure.”
In short, three elements: fire, earth, and water, are all that exist, but that, among these, “fire” was the primary element, controlling and modifying the other two, and that everything is in a continuous state of flux, or change, and war and strife between opposites is the eternal condition of the universe.
An implicit assumption in this logic is underlying premise that movement and change would require space or a “void”, or space devoid of the three elements. (Ѻ)
In circa 480BC, Greek philosopher Parmenides (510-450BC), head of the so-called Eleatic school, whose members included Melissus (500-440BC) and Zeno of Elea (495-430BC), the latter a said “pupil” of Leucippus, in reaction to materialism philosophers, in what some have referred to as an "attack" (Ѻ) on Heraclitus, argued that all that existed was some type of immovable “being”, and concordantly that “non-being” or void was impossible—the following fragment from Melissus gives the gist of this argument: 
“There is absolutely NO void. For void is not-being and the nothing could not exist. And it does not move. For it cannot move in any direction. But it is full. For if there were void, it would move into that void, but since there is no void it has nothing to move into.”
The following is another example statement:
“Being is unbegotten, indestructible, whole, eternally one, immovable and infinite. With it there is no was nor shall be; the whole is forever now, one and continuous.”— Parmenides (c.460BC), Fragment; cited by: Henry Bray (1910) in The Living Universe (pg. 251) 
In 1908, Polish-born French chemist and philosopher Emile Meyerson published Identity and Reality, said to be some type of Heraclitus vs Parmenides reconciliation aiming work. 
In 1942-43, at the University of Feiburg, Martin Heidegger gave a winter semester lecture course on Parmenides; and in the winter semester of 1966-67, conducted a seminar on the fragments of Heraclitus; together, the set is said to outline the contrasting views of both philosopher on the subjects of truth, being, and understanding. 
1. Meyerson, Émile. (1908). Identity and Reality (Identité et Réalite) (ch. 8: Carnot’s principle, pgs. 259-90). Routledge.
2. (a) Heidegger, Martin. (1943). Parmenides (translators: Andre Schuwer and Richard Rojcewicz). Indiana University Press, 1992.
(b) Heidegger, Martin and Fink, Eugen. (1967). Heraclitus Seminar (translator: Charles Seibert). Northwestern University Press, 1993.
3. Bray, Henry T. (1910). The Living Universe (pg. 251). Truro Publishing Co., 1920.
4. Algra, Keimpe. (1995). Concepts of Space in Greek Thought (pg. 43). Brill.
● Anon. (2013). “Heraclitus vs Parmenides: the Problem of Change” (Ѻ), True Forms, WordPress.com, Jul 16.
● Anons. (2013). “Discussing the Heraclitus and Parmenides” (Ѻ), Tokyo Philosophical Society, Jun 26.
● Heraclitus and Parmenides – ThreeMinutePhilosophy.com.
● Heraclitus and Parmenides (2002) – PhilosophyForums.com.