Board Thread:Warhammer 40k General Discussion/@comment-14745711-20130821214539/@comment-8881468-20130901192231

to quote the article  (which you should have taken a look at ages ago before going on)

"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."

And that means:

Physical well being, pursuit of own ideals/happiness (as long as no conflict with the idea of greater good), religeous freedom, free trade, unhindered research, peaceful coexistence with other races and so on and so forth