Elemental thought

摘要

Forget everything you know about science. Forget -just for a moment - the periodic table with its protons, neutrons and electrons. Forget about gene pools and DNA. Now, with modern science out of your mind, define nature as simply as you can. What is the world made of? If you answer something like, "earth, water, air and fire," then you are thinking like the Greek philosopher Empedocles. In the 5th century BC, Empedocles proposed that all worldly substances were composed of these four elements. Aristotle based his own natural philosophy on this notion, theorising that the ratio of these elements in matter determined substance and form. It was not until two thousand years later that scientists began to believe otherwise. In 1776, Joseph Priestley of England discovered that water was made of two smaller elements. A few years later, his French colleague, Antoine-Laurent Lavoisier, deduced that water's "oxygen" - as Priestley termed it - was the active component of air. Lavoisier, considered the father of modem chemistry, offered theories of oxygen's role in combustion and respiration, and invented a new terminology to suggest a logic of chemical reactions.