Aristotle disbelieved the ancient Greek theory of atoms being of different sizes, regular geometric shapes and beig in constant motion. He didn't think atoms could be in constant motion in a void. He developed the theroy that all matter consisted of four elements: Earth, Air, Water and Fire. There were also four qualities: dryness, hotness, coldness, and moistness. Fire was dry and hot, water was moist and cold, etc. Each of these elements move naturally in a line to their "proper place," where it will be at rest. Aristotle's theory also had two forces: conflict and harmony. Conflict was thought to cause bad things, and harmony good things. Aristotle also believed that the heavens were made of a fifth, superior element named aither. Aristotle's theory was used for almost 2000 years, until after the scientific revolution, when other theories prevailed.