Arche is a Greek word with primary senses "beginning", "origin" or "source of action", and later "first principle" or "element". By extension, it may mean "first place", "method of government", "empire, realm", "authorities", "command". The first principle or element corresponds to the "ultimate underlying substance" and "ultimate undemonstrable principle". In the philosophical language of the archaic period, arche designates the source, origin or root of things that exist. In ancient Greek philosophy, Aristotle foregrounded the meaning of arche as the element or principle of a thing, which although undemonstrable and intangible in itself, provides the conditions of the possibility of that thing.
