Quintessence

The purest form of a perfume is sometimes called quintessence, as though the fragrance was five ("quinta") times distilled. Figuratively, quintessence means the most essential part of an idea. Ancient philosophers thought that all matter took one of four forms - earth, air, fire, water. Pythagoreans and medieval alchemists proposed a fifth element, or "quinta essentia." They believed it permeated all things and was the substance of the heavenly bodies. No alchemist succeeded in extracting this fifth element, however, so since 1570, "quintessence" has meant the quality that most characterizes a substance or notion.