Leucippus, 5th cent. B.C., Greek philosopher. Aristotle believed that Leucippus inspired the atomistic theory with which Democritus is identified. Little is known about Leucippus.

Atomism, philosophic concept of the nature of the universe, holding that the universe is composed of invisible, indestructible material particles. The theory was first advanced in the 5th cent...

Epicurus, 341–270 B.C., Greek philosopher, b. Samos; son of an Athenian colonist. He claimed to be self-taught, although tradition states that he was schooled in the systems of Plato and Democ...

Gassendi, Pierre, 1592–1655, French philosopher and scientist. A teacher and priest, Gassendi taught at Digne, Aix, and the Royal College at Paris and held several church offices. He ranked wi...

Abdera or Avdira, town, NE Greece, in Thrace, near the mouth of the Mesta River. It is a small agricultural settlement. Founded (c.650 B.C.) by colonists from Clazomenae, it was destroyed by t...

Burton, Robert, 1577–1640, English clergyman and scholar, b. Leicestershire, educated at Oxford. He served as librarian at Christ Church, Oxford, all his life; in addition he was vicar of St. ...

Lucretius (Titus Lucretius Carus), c.99 B.C.–c.55 B.C., Roman poet and philosopher. Little is known about his life. A chronicle of St. Jerome speaks of the loss of his reason through taking a ...

Materialism, in philosophy, a widely held system of thought that explains the nature of the world as entirely dependent on matter, the fundamental and final reality beyond which nothing need b...

Skepticism [Gr.,=to reflect], philosophic position holding that the possibility of knowledge is limited either because of the limitations of the mind or because of the inaccessibility of its o...

Matter, anything that has mass and occupies space. Matter is sometimes called koinomatter (Gr. koinos=common) to distinguish it from antimatter, or matter composed of antiparticles. The genera...