who thought atoms and the void comprised all of reality
Parmenides of Elea
title: History of molecular theory text: History of molecular theory In chemistry, the history of molecular theory traces the origins of the concept or idea of the existence of strong chemical bonds between two or more atoms. The modern concept of molecules can be traced back towards pre-scientific and Greek philosophers such as Leucippus and Democritus who argued that all the universe is composed of atoms and voids. Circa 450 BC Empedocles imagined fundamental elements (fire (), earth (), air (), and water ()) and "forces" of attraction and repulsion allowing the elements to interact. Prior to this, Heraclitus had claimed that fire or change was title: Epicurus text: he maintained that people should still behave ethically because amoral behavior will burden them with guilt and prevent them from attaining "ataraxia". Like Aristotle, Epicurus was an empiricist, meaning he believed that the senses are the only reliable source of knowledge about the world. He derived much of his physics and cosmology from the earlier philosopher Democritus ( 460– 370 BC). Like Democritus, Epicurus taught that the universe is infinite and eternal and that all matter is made up of extremely tiny, invisible particles known as "atoms". All occurrences in the natural world are ultimately the result of atoms moving title: Universe text: be earth, water, air and fire. His four-element model became very popular. Like Pythagoras, Plato believed that all things were composed of number, with Empedocles' elements taking the form of the Platonic solids. Democritus, and later philosophers—most notably Leucippus—proposed that the Universe is composed of indivisible atoms moving through a void (vacuum), although Aristotle did not believe that to be feasible because air, like water, offers resistance to motion. Air will immediately rush in to fill a void, and moreover, without resistance, it would do so indefinitely fast. Although Heraclitus argued for eternal change, his contemporary Parmenides made the radical title: Atom text: idea, appearing in many ancient cultures such as Greece and India. The word "atom" (; ""), meaning "uncuttable", was coined by the ancient Greek philosophers Leucippus and his pupil Democritus ( 460 – 370 BC). Democritus taught that atoms were infinite in number, uncreated, and eternal, and that the qualities of an object result from the kind of atoms that compose it. Democritus's atomism was refined and elaborated by the later philosopher Epicurus (341–270 BC). During the Early Middle Ages, atomism was mostly forgotten in western Europe, but survived among some groups of Islamic philosophers. During the twelfth century, atomism title: History of science in classical antiquity text: matter is a continuous substance. Two Greek philosophers, Leucippus (first half of the 5th century BC) and Democritus of Abdera (lived about 410 BC) came up with the notion that there were two real entities: atoms, which were small indivisible particles of matter, and the void, which was the empty space in which matter was located. Although all the explanations from Thales to Democritus involve matter, what is more important is the fact that these rival explanations suggest an ongoing process of debate in which alternate theories were put forth and criticized. Xenophanes of Colophon prefigured paleontology and geology as