Cognition covers the arts of problem solving. The Chaos field of study covers any activity that studies Chaos in order to manifest the material. Chaos is the study of Random, and the concept of the Void. Some have argued that this is the source of the Dark Side. The word χάος did not mean "disorder" in classical-period ancient Greece. It meant "the primal emptiness, space" (see Chaos (mythology)). Chaos is derived from the Proto-Indo-Euopean root ghn or ghen meaning "gape, be wide open": compare "chasm" (from Ancient Greek χάσμα, a cleft, slit or gap), and Anglo-Saxon gānian ("yawn"), geanian, ginian ("gape wide"); see also Old Norse Ginnungagap. Due to people misunderstanding early Christian uses of the word, the meaning of the word changed to "disorder". (The Ancient Greek for "disorder" is ταραχή.)