Democritus developed an atomic theory to explain the nature of the universe. He held that all things, including the mind and the soul, are composed of infinitesimal bits of matter that cannot be divided into anything smaller. He named the bits of matter atoma, a Greek word meaning indivisible. Democritus believed that countless atoms of various sizes and shapes are in continuous motion in a void, or empty space. The atoms combine in different ways to form such things as plants, men, the earth, and the heavens. These may pass out of existence if their atoms are dispersed, but the atoms themselves are indestructible.
Considered the forerunner of modern mechanistic science, Democritus has been called the first materialist. Because of his belief that cheerfuhless and moderation are the keys to a happy life, he has also become known as the Laughing Philosopher.
