Thomas Young: The last man who knew everything?

Abstract The polymath Thomas Young is best known as a physicist for his double-slit experiment showing the interference of light and hence its wave nature, published in 1807. However, Young had no formal training in physics and was instead a qualified physician. His first scientific research in the 1790s was on the human eye, which led him to his three-colour theory of how the retina responds to light, published in 1802 and finally confirmed experimentally in 1959. In other words, Young’s passion to understand the physiology of vision led to his subsequent fascination with the physics of light—an important example of the value of polymathy. Later his passion for ancient and modern languages—he coined the term ‘Indo-European’ in 1813—led to his fascination with the Egyptian hieroglyphs and his pioneering decipherment of the Rosetta Stone in 1815-1819. This paper samples Young’s amazing range and also considers polymathy’s advantages and disadvantages, then and now.