- "A Tau chooses neither its caste nor its True Name. We are blood born to the first and borne by blood to the second, named for what we have done and might yet do. And like ourselves, our true names are not carved in stone."
- — The Tau’va
The Greater Good, or Tau'va (literally the "Good Greater" in the Tau Lexicon language), is the founding religio-philosophical principle of modern Tau society which holds that all sentient beings should strive to ensure the greatest good for the greatest number of beings in the galaxy. The Tau'va is based on the Tau caste system and is designed to allow for the advancement of the entire Tau society towards a more successful, prosperous and peaceful existence in the future without much of the violent conflict that marked earlier Tau history.
The Greater Good was first introduced to the Tau during the Mont'au ("Death Age"), the long period of civil war fought between the different Tau cities and clans on their homeworld of T'au before the formation of the unified Tau Empire under the guidance of the Ethereal caste. It was during this time that the first Ethereals came to the other Tau and united the Tau tribes with the philosophy of the Greater Good. This concept involves the pursuit of perfect societal harmony and combines the particular strengths of each Tau caste to counter the many weaknesses and divisions their culture once possessed. Within only a few years after the Ethereals first revealed themselves, Tau culture was dominated by the pursuit of the Greater Good and the Tau Empire began its long march towards the development of advanced, starfaring technology.
The philosophy of the Greater Good now guides the Tau in their attempts to conquer the rest of the galaxy and unite all the intellignt races in pursuit of the Greater Good. The philosophy forces the Tau to both desire to expand their empire for the Greater Good, and to absorb other intelligent races and their cultures into their own, which could ultimately have disastrous effects upon their ability to actually keep their newborn interstellar empire united. The ideal of the Greater Good appeals to some of the other intelligent races of the galaxy, and stranded units of the Imperial Guard are said to have surrendered themselves to the Tau and now live in the Tau Empire, where humans are known as the Gue'vesa. Such people are considered traitors and heretics by the Imperium of Man. During any conflict against other intelligent species, Tau Commanders often urge the enemy leaders to stop resisting the Tau Empire since they will be allowed to retain their own individual faiths and philosophical beliefs as long as they are compatible with the Greater Good.
- Codex: Tau (3rd Edition)
- Codex: Tau Empire (4th Edition)
- Warhammer 40,000: Dawn of War - Dark Crusade