It can be hard to express liberating insights without sounding banal. Perhaps mindful of the limits of words, some of the earliest teachings on oneness say it is conveyed by a single syllable. Chanting Om is said to teach the meaning of all of the Upanishads. This message is meant to be realised, not discussed, but some interpretive guidance is helpful. The first author to offer it as a philosophy was Gaudapada, whose verses - or Karika - on the Mandukya Upanishad laid the foundations of Advaita Vedanta, a widely influential system of ideas.