Heraclitus is recognized as one of the earliest dialectical philosophers with his acknowledgment of the universality of change and development through internal contradictions, as in his statements:
"By cosmic rule, as day yields night, so winter summer, war peace, plenty famine. All things change. Air penetrates the lump of myrrh, until the joining bodies die and rise again in smoke called incense."
"Men do not know how that which is drawn in different directions harmonises with itself. The harmonious structure of the world depends upon opposite tension like that of the bow and the lyre."
"This universe, which is the same for all, has not been made by any god or man, but it always has been, is, and will be an ever-living fire, kindling itself by regular measures and going out by regular measures"
He is famous for (allegedly) expressing the notion that no man can enter the same river twice:
"Ποταμοῖς τοῖς αὐτοῖς ἐμβαίνομέν τε καὶ οὐκ ἐμβαίνομεν, εἶμέν τε καὶ οὐκ εἶμεν."
"We both step and do not step in the same rivers. We are and are not."
A modern translation of this quote may better illustrate how Aristotle's later position on the illogic of contradiction was not a direct refutation of Heraclitus:
"No man ever steps in the same river twice, for it is not the same river and he is not the same man."
The idea of the logos is also credited to him, as he proclaims that everything originates out of the logos. Further, Heraclitus said "I am as I am not", and "He who hears not me but the logos will say: All is one." Heraclitus held that an explanation of change was foundational to any theory of nature. This view was strongly opposed by Parmenides, who said that reality was permanent and unchanging. According to Lavine, Parmenides asked, "How can a thing change into something else? How can it be and not be?" According to Parmenides, change is merely an illusion.
His promotion of change also led Heraclitus to believe that conflict (e.g., ἀγών agon in Greek) is necessary for change to occur and to argue against Homer: "War is the father of all and the king of all" and "Every animal is driven to pasture with a blow."
His view on the random chance inherent in the universe[dubious ]. is famously the direct opposite of Einstein's (in which he stated "God does not play dice with the universe"): "Time is a child moving counters in a game; the kingly power is a child's."
The Heraclitean emphasis on the nature of things and existence as one of constant change, expressed with language of polarity, is particularly reminiscent of another ancient philosophical tradition, that of Taoism: the Tao (or "the Way") often refers to a space-time sequence, and is similarly expressed with seemingly-contradictory language (e.g., "The Way is like an empty vessel / that may still be drawn from / without ever needing to be filled"). Indeed, parallels have been drawn between the fundamental concepts of the logos (as it was understood during Heraclitus's time) and the Tao.
There are several legendary stories about Heraclitus, especially concerning his eventual death from illness, including his supposed attempt to stave off death using dung and ignoring doctors. These mostly stem from mis-interpretations of the metaphors in his fragments and an attempt to construct a narrative based on these fragments.
There is a popular misconception that it was the famous philosopher whose death was lamented in an epitaph by Callimachus; the philosopher is thought to have died nearly two centuries before the head of the Alexandrian Library was born, and in Ephesus, far from Alexandria. The Heraclitus spoken of in the original as the speaker's "Halicarnasian friend" is probably Heraclitus of Halicarnassus (in Caria). The 'Nightingales' referred to below were a collection of poems. The translation by William Johnson Cory is a masterpiece in its own right. Included in his Ionica collection, it was set for choir by Charles Villiers Stanford:
They told me, Heraclitus, they told me you were dead,
They brought me bitter news to hear and bitter tears to shed.
I wept as I remembered how often you and I
Had tired the sun with talking and sent him down the sky.
And now that thou art lying, my dear old Carian guest,
A handful of grey ashes, long long ago at rest,
Still are thy pleasant voices, thy nightingales, awake;
For Death, he taketh all away, but them he cannot take.
The interpretation of Heraclitus' work is diverse, partly due to the fragmentary nature of his statements, and partly due to the perspectives of his interpreters. Although many philosophers have acknowledged his influence, including Plato and Aristotle, his concept of Becoming, in which ontological opposites are seen as fundamentally interrelated, is central to his philosophy. More particularly, he wrote: "Opposition brings concord. Out of discord comes the fairest harmony" (frag. 98; trans William Harris). Both Plato and Aristotle would have disagreed. Plato believed that each thing has one unchanging essence. Aristotle was the first philosopher to formally state the law of non-contradiction as "one cannot say of something that it is and that it is not in the same respect and at the same time." Therefore Aristotelian logic is in direct opposition to logos, because statements like "I am as I am not" clearly violate the law of non-contradiction.
- Plato understood Heraclitus as the theorist of "panta rhei" (universal flux), as contrasted with Parmenides' conception of a fixed and stable reality. As a point of clarification, Heraclitus does not appear to have proposed that reality as a whole is unstable, but since Heraclitus recognized nothing but existence itself as stable (existence being one), his philosophy came into conflict with Plato's inclination toward multiple universal absolutes. Plato's theory of forms has been seen as a response to Heraclitus.
- Aristotle saw Heraclitus as "a material monist who derived the entire physical world from fire as its underlying element," and also as a kind of dialectical philosopher of harmonic opposition. Origen and Hippolytus of Rome also appear to have adopted the "dialectical" interpretation.
- The Stoics based their cosmology on Aristotle's materialistic interpretation of Heraclitus, and interpreted the Logos as transcendent Reason, immanent in the world. Kahn sees the Stoics as "the true Heracliteans of antiquity."
- Heraclitus' idea of the Logos was very influential on Jewish philosophers such as Philo of Alexandria, who connected it to Jewish notions of "Wisdom personified" as God's creative principle. Philo uses the term Logos throughout his treatises on Hebrew Scripture in a manner clearly influenced by Heraclitus' work.
- The author of the fourth Gospel, the Gospel of St. John (traditionally ascribed to John the Apostle) uses the term Logos throughout the first chapter of his book to describe the pre-human existence of Jesus as the Word (Logos) of God: "In the beginning was the Logos (Word), and the Logos was with God, and the Logos was God. All things were made by him; and without him was not any thing made that was made....And the Logos was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth." (John 1:1, 3, 14)
- Friedrich Nietzsche saw Heraclitus from a process perspective: "Insofar as the senses show becoming, passing away, and change, they do not lie." Heraclitus is commonly recognized as the first advocate of process philosophy the West, and a direct precursor to Georg Wilhelm Friedrich Hegel.
- Alfred North Whitehead, known for having seen all of Western philosophy as the legacy of Plato, saw Heraclitus as Plato did, yet referred to both the forms of Plato and the flux model of Heraclitus in developing his own thoughts on process philosophy.
- Oswald Spengler wrote his doctoral thesis on Heraclitus, and his notion of eternal war was very strongly influenced by Heraclitus, who saw conflict as "the father of all things."
- Martin Heidegger in his 1943/44 lectures expansively discusses Heraclitus in the context of "the origin of occidental thought" and "logic - Heraclitus' teaching of logos", and credits the very coining of the term "philosophy" to Heraclitus, evidently because of Heraclitus' high regard for "sophon" (wisdom; what is wise).
- Karl Popper accused Heraclitus as having played a part in laying the foundations for a closed society. In particular, Popper concludes that Heraclitus relativises moral values, quoting Heraclitus: "The good and the bad are identical", relating to Heraclitus's theory of the unity of opposites. Popper also alleges Heraclitus of having formulated a historicist doctrine based on the "justice of war and the verdict of history a tribalist and romantic ethic of Fame, Fate, and the superiority of the Great Man".
- Carl Jung developed the psychological concept of enantiodromia (in a manner similar to Heraclitus' usage) to illustrate his notion that whenever an individual forms an asymmetrical, conscious ideation as fundamentally predominant, for example, "masculine" values and suppositions of a father archetypalfigure, there will necessarily be opposing forces, and that they will make themselves apparent within the unconscious in various ways as a means to maintain an individual's psychic balance.
Parmenides of Elea (Greek: Παρμενίδης ο Έλεάτης, early 5th century BC) was an ancient Greek philosopher born in Elea, a Hellenic city on the southern coast of Italy. Parmenides was a student of Ameinias and the founder of the School of Elea, which also included Zeno of Elea and Melissus of Samos. According to Plato, Parmenides had been the erastes of Zeno when the latter had been a youth. 
Parmenides is one of the most significant of the pre-Socratic philosophers. His only known work, conventionally titled 'On Nature' is a poem, which has only survived in fragmentary form. Approximately 150 lines of the poem remain today; reportedly the original text had 3,000 lines. It is known, however, that the work originally divided into three parts:
- A proem, which introduced the entire work,
- A section known as "The way of truth" (aletheia), and
- A section known as "The way of appearance/opinion" (doxa).
The proem is a narrative sequence in which the narrator travels "beyond the beaten paths of mortal men" to receive a revelation from an unnamed goddess (generally thought to be Persephone) on the nature of reality. Aletheia, an estimated 90% of which has survived, and doxa, most of which no longer exists, are then presented as the spoken revelation of the goddess without any accompanying narrative. He also discovered that the earth was round, whilst watching an eclipse ... he noticed the earth's shadow was curved so therefore the earth had to be round.
 Interpretations of Parmenides
The traditional interpretation of Parmenides' work is that he argued that the every-day perception of reality of the physical world (as described in doxa) is mistaken, and that the reality of the world is 'One Being' (as described in aletheia): an unchanging, ungenerated, indestructible whole. Under 'way of seeming', Parmenides set out a contrasting but more conventional view of the world, thereby becoming an early exponent of the duality of appearance and reality. For him and his pupils the phenomena of movement and change are simply appearances of a static, eternal reality.
Parmenides' philosophy is presented in the form of poetry. The philosophy he argued was, he says, given to him by a goddess, though the "mythological" details in Parmenides' poem do not bear any close correspondence to anything known from traditional Greek mythology:
- Welcome, youth, who come attended by immortal charioteers and mares which bear you on your journey to our dwelling. For it is no evil fate that has set you to travel on this road, far from the beaten paths of men, but right and justice. It is meet that you learn all things - both the unshakable heart of well-rounded truth and the opinions of mortals in which there is not true belief.
It is with respect to this religious/mystical context that recent generations of scholars such as Alexander P. Mourelatos, Charles H. Kahn, and the controversial Peter Kingsley have begun to call parts of the traditional, rational logical/philosophical interpretation of Parmenides into question. According to Peter Kingsley Parmenides practiced iatromancy. It has been claimed, for instance, that previous scholars placed too little emphasis on the apocalyptic context in which Parmenides frames his revelation. As a result, traditional interpretations have put Parmenidean philosophy into a more modern, metaphysical context to which it is not necessarily well suited, which has led to misunderstanding of the true meaning and intention of Parmenides' message. The obscurity and fragmentary state of the text, however, renders almost every claim that can be made about Parmenides extremely contentious, and the traditional interpretation has by no means been completely abandoned.
Parmenides' considerable influence on the thinking of Plato is undeniable, and in this respect Parmenides has influenced the whole history of Western philosophy, and is often seen as its grandfather. Even Plato himself, in the Sophist, refers to the work of "our Father Parmenides" as something to be taken very seriously and treated with respect. In the Parmenides the Eleatic philosopher, which may well be Parmenides himself, and Socrates argue about dialectic. In the Theaetetus, Socrates says that Parmenides alone among the wise (Protagoras, Heraclitus, Empedocles, Epicharmus, and Homer) denied that everything is change and motion.
Parmenides is credited with a great deal of influence as the author of an "Eleatic challenge" that determined the course of subsequent philosophers' enquiries. For example, the ideas of Empedocles, Anaxagoras, Leucippus, and Democritus have been seen as in response to Parmenides' arguments and conclusions.
 Arguments by Parmenides
The Eleatics were a school of pre-Socratic philosophers at Elea, a Greek colony in Campania, Italy. The group was founded in the early fifth century BCE by Parmenides. Other members of the school included Zeno of Elea and Melissus of Samos. Xenophanes is sometimes included in the list, though there is some dispute over this
The school took its name from Elea, a Greek city of lower Italy, the home of its chief exponents, Parmenides and Zeno. Its foundation is often attributed to Xenophanes of Colophon, but, although there is much in his speculations which formed part of the later Eleatic doctrine, it is probably more correct to regard Parmenides as the founder of the school.
Xenophanes had made the first attack on the mythology of early Greece in the middle of the 6th century, including an attack against the whole anthropomorphic system enshrined in the poems of Homer and Hesiod. In the hands of Parmenides this spirit of free thought developed on metaphysical lines. Subsequently, either because its speculations were offensive to the contemporary thought of Elea, or because of lapses in leadership, the school degenerated into verbal disputes as to the possibility of motion and other such academic matters. The best work of the school was absorbed into Platonic metaphysics.
The Eleatics rejected the epistemological validity of sense experience, and instead took mathematical standards of clarity and necessity to be the criteria of truth. Of the members, Parmenides and Melissus built arguments starting from indubitably sound premises. Zeno, on the other hand, primarily employed the reductio ad absurdum, attempting to destroy the arguments of others by showing their premises led to contradictions (Zeno's paradoxes).
The main doctrines of the Eleatics were evolved in opposition to the theories of the early physicalist philosophers, who explained all existence in terms of primary matter, and to the theory of Heraclitus, which declared that all existence may be summed up as perpetual change. The Eleatics maintained that the true explanation of things lies in the conception of a universal unity of being. According to their doctrine, the senses cannot cognize this unity, because their reports are inconsistent; it is by thought alone that we can pass beyond the false appearances of sense and arrive at the knowledge of being, at the fundamental truth that the All is One. Furthermore, there can be no creation, for being cannot come from non-being, because a thing cannot arise from that which is different from it. They argued that errors on this point commonly arise from the ambiguous use of the verb to be, which may imply existence or be merely the copula which connects subject and predicate.
Though the conclusions of the Eleatics were rejected by the later Presocratics and Aristotle, their arguments were taken seriously, and they are generally credited with improving the standards of discourse and argument in their time. Their influence was likewise longlasting -- Gorgias, a Sophist, argued in the style of the Eleatics in his work "On Nature or What Is Not," and Plato acknowledged them in the Parmenides, the Sophist and the Politicus. Furthermore, much of the later philosophy of the ancient period borrowed from the methods and principles of the Eleatics.