Alchemy. The English word alchemy comes from the Arabic word al-chemi (the change), which is also the root of the English word chemistry. The roots of alchemy can be traced to ancient cultures ranging from China to Egypt, where it developed from a mixture of religion, philosophy, and science. While modern people have often dismissed alchemy as an occult (or magical) pseudoscience, historians of science have come to realize that it was a serious form of scientific research. In fact, alchemists made important contributions to chemistry, medicine, and physics.

Scientific Method. Perhaps their most valuable contribution was what is now known as the scientific method, which was a revolutionary development when the Arab alchemists introduced it in the ninth century. Alchemists learned that by doing certain things to natural substances— such as mixing them, heating them, or distilling them—they could...