Changing one element into another. Plato defined four elements the earth, air, fire, and water basic constituents of the universe. He identified each with a regular solid figure the earth with the cube, air with the octahedron, fire with the tetrahedron, and water with the icosahedron. Any of the last three could be broken into its equilateral triangle faces and reassembled as one of the others transmutation of the elements. Aristotle had a similar theory but dispensed with the solids, replacing them with hot and cold, wet and dry. Earth was composed of cold and dry, water of cold and wet, air of hot and wet, fire of hot and dry. Again the constituents of one could be reassembled to form another. Evaporating water, for example, was explained by adding heat to cold and wet (water) and turning it into hot and wet (air).
This theory was adopted by the Arabs, who brought it into Europe and was accepted by medieval alchemists, who wished to change other metals into gold. A number of scientists, including Philippus Paracelsus (1493— 541) and Sir Isaac Newton, spent much time searching for the philosopher’s stone, which was necessary for the transmutation.