Democritus in the context of "Chance and Necessity"

Pre-Socratic philosophy, also known as early Greek philosophy, is ancient Greek philosophy before Socrates. Pre-Socratic philosophers were mostly interested in cosmology, the beginning and the substance of the universe, but the inquiries of these early philosophers spanned the workings of the natural world as well as human society, ethics, and religion. They sought explanations based on natural law rather than the actions of gods. Their work and writing has been almost entirely lost. Knowledge of their views comes from testimonia, i.e. later authors' discussions of the work of pre-Socratics. Philosophy found fertile ground in the ancient Greek world because of the close ties with neighboring civilizations and the rise of autonomous civil entities, poleis.

Pre-Socratic philosophy began in the 6th century BC with the three Milesians: Thales, Anaximander, and Anaximenes. They all attributed the arche (a word that could take the meaning of "origin", "substance" or "principle") of the world to, respectively, water, apeiron (the unlimited), and air. Another three pre-Socratic philosophers came from nearby Ionian towns: Xenophanes, Heraclitus, and Pythagoras. Xenophanes is known for his critique of the anthropomorphism of gods. Heraclitus, who was notoriously difficult to understand, is known for his maxim on impermanence, ta panta rhei, and for attributing fire to be the arche of the world. Pythagoras created a cult-like following that advocated that the universe was made up of numbers. The Eleatic school (Parmenides, Zeno of Elea, and Melissus) followed in the 5th century BC. Parmenides claimed that only one thing exists and nothing can change. Zeno and Melissus mainly defended Parmenides' opinion. Anaxagoras and Empedocles offered a pluralistic account of how the universe was created. Leucippus and Democritus are known for their atomism, and their views that only void and matter exist. The Sophists advanced philosophical relativism. The Pre-Socratics have had significant impact on several concepts of Western philosophy, such as naturalism and rationalism, and paved the way for scientific methodology.

Ionic or Ionian Greek (Ancient Greek: Ἰωνική, romanized: Iōnikḗ) was a subdialect of the Eastern or Attic–Ionic dialect group of Ancient Greek. The Ionic group traditionally comprises three dialectal varieties that were spoken in Euboea (West Ionic), the northern Cyclades (Central Ionic), and from c. 1000 BC onward in Asiatic Ionia (East Ionic), where Ionian colonists from Athens founded their cities. Ionic was the base of several literary language forms of the Archaic and Classical periods, both in poetry and prose. The works of Homer and Hesiod are among the most popular poetic works that were written in a literary form of the Ionic dialect, known as Epic or Homeric Greek. The oldest Greek prose, including that of Heraclitus, Herodotus, Democritus, and Hippocrates, was also written in Ionic. By the end of the 5th century BC, Ionic was supplanted by Attic, which had become the dominant dialect of the Greek world.

Heraclitus (/ˌhɛrəˈklaɪtəs/; Ancient Greek: Ἡράκλειτος Hērákleitos; fl. c. 500 BC) was an ancient Greek pre-Socratic philosopher from the city of Ephesus, which was then part of the Persian Empire. He exerts a wide influence on Western philosophy, both ancient and modern, through the works of such authors as Plato, Aristotle, Georg Wilhelm Friedrich Hegel, Friedrich Nietzsche, and Martin Heidegger.

Little is known of Heraclitus's life. He wrote a single work, of which only fragments survive. Even in ancient times, his paradoxical philosophy, appreciation for wordplay, and cryptic, oracular epigrams earned him the epithets "the dark" and "the obscure". He was considered arrogant and depressed, a misanthrope who was subject to melancholia. Consequently, he became known as "the weeping philosopher" in contrast to the ancient atomist philosopher Democritus, who was known as "the laughing philosopher".

Western Thrace (Greek: Δυτική Θράκη, IPA: [ðitiˈci ˈθɾaci]), also known as Greek Thrace or Aegean Thrace, is a geographical and historical region of Greece, between the Nestos and Evros rivers in the northeast of the country; East Thrace, which lies east of the river Evros, forms the European part of Turkey, and the area to the north, in Bulgaria, is known as Northern Thrace.

Inhabited since Paleolithic times, it has been under the political, cultural and linguistic influence of the Greek world since the classical era; Greeks from the Aegean islands extensively colonized the region (especially the coastal part) and built prosperous cities such as Abdera (home of Democritus, the 5th-century BC philosopher who developed an atomic particle theory, and of Protagoras, a leading sophist) and Sale (near present-day Alexandroupolis). Under the Byzantine Empire, Western Thrace benefited from its position close to the imperial heartland and became a center of medieval Greek commerce and culture; later, under the Ottoman Empire, a number of Muslims settled there, marking the birth of the Muslim minority of Greece.

Leucippus (/luːˈsɪpəs/; Λεύκιππος, Leúkippos; fl. 5th century BCE) was a pre-Socratic Greek philosopher. He is traditionally credited as the founder of atomism, which he developed with his student Democritus. Leucippus divided the world into two entities: atoms, indivisible particles that make up all things, and the void, the nothingness that exists between the atoms. He developed his philosophy as a response to the Eleatics, who believed that all things are one and the void does not exist. Leucippus's ideas were influential in ancient and Renaissance philosophy. Leucippus was the first Western philosopher to develop the concept of atoms, but his ideas only bear a superficial resemblance to modern atomic theory.

Leucippus's atoms come in infinitely many forms and exist in constant motion, creating a deterministic world in which everything is caused by the collisions of atoms. Leucippus described the beginning of the cosmos as a vortex of atoms that formed the Earth, the Sun, the stars, and other celestial bodies. As Leucippus considered both atoms and the void to be infinite, he presumed that other worlds must exist as cosmoses are formed elsewhere. Leucippus and Democritus described the soul as an arrangement of spherical atoms, which are cycled through the body through respiration and create thought and sensory input.

In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model recognizes seventeen distinct particles—twelve fermions and five bosons. As a consequence of flavor and color combinations and antimatter, the fermions and bosons are known to have 48 and 13 variations, respectively. These 61 elementary particles include electrons and other leptons, quarks, and the fundamental bosons. Subatomic particles such as protons or neutrons, which contain two or more elementary particles, are known as composite particles.

Ordinary matter is composed of atoms, themselves once thought to be indivisible elementary particles. The name atom comes from the Ancient Greek word ἄτομος (atomos) which means indivisible or uncuttable. Despite the theories about atoms that had existed for thousands of years, the factual existence of atoms remained controversial until 1905. In that year, Albert Einstein published his paper on Brownian motion, putting to rest theories that had regarded molecules as mathematical illusions. Einstein subsequently identified matter as ultimately composed of various concentrations of energy.

Epicureanism is a system of philosophy founded in 307 BCE and based upon the teachings of Epicurus, an ancient Greek philosopher. Epicurus was an atomist and materialist, following in the steps of Democritus. His materialism led him to religious skepticism and a general attack on superstition and divine intervention. Epicureanism was originally a challenge to Platonism, and its main opponent later became Stoicism. It is a form of hedonism insofar as it declares pleasure to be its sole intrinsic goal. However, the concept that the absence of pain and fear constitutes the greatest pleasure, and its advocacy of a simple life, make it very different from hedonism as colloquially understood.

Following the Cyrenaic philosopher Aristippus, Epicurus believed that the greatest good was to seek modest, sustainable pleasure in the form of a state of ataraxia (tranquility and freedom from fear) and aponia (the absence of bodily pain) through knowledge of the workings of the world and limiting desires. Correspondingly, Epicurus and his followers generally withdrew from politics because it could lead to frustrations and ambitions that would conflict with their pursuit of virtue and peace of mind.

Hegesistratus (Ancient Greek: Ἡγησίστρατος) is an ancient Greek name. Some people with this name were:

1. A Greek diviner for Mardonius during the Greco-Persian Wars. Originally an Elean, he had been captured by the Spartans and put in bonds. He escaped by cutting off a piece of his own foot and replaced it with a wooden one; however, he was captured again at Zacynthus and put to death. This story is mentioned in the ninth book (chapter 37) of the Histories written by Herodotus.
2. An emissary from Samos to the Greeks before the Battle of Mycale.
3. A despot of Sigeum.
4. An Ephesian committed a murder in his family, and fled to Delphi; on consulting the oracle what place to settle in, the answer was, that when he should come to a place where he should see the country people dancing with garlands of olive-leaves, he should settle there. He travelled and found what the oracle told him, and there built the city Elaeus.
5. Democritus was the son of Hegesistratus, though some say of Athenocritus, and others of Damasippus.
6. The governor of Miletus, during the Siege of Miletus by Alexander the Great.