Board Thread:Warhammer 40k General Discussion/@comment-174.29.74.18-20130615110043/@comment-3580035-20130620043842

It has clearly stated multiple times in various sources that the Tau are NOT a psychic race. The Ethereals also do NOT use psychic powers to control the Tau, nor are they psychic in any way. They also do not use pheromones, as can be proven through logic and historical accounts. It is most likely that the Tau revere them for saving them from the Mon'tau.

There has never been a recorded incident of Tau turning to Chaos, and the Ethereals encourge all forms of research. The best example is the Fall of Medusa V campaign, where the whole purpose of the Tau being there was to research the Warp (and eventually finding out it ain't worth the trouble)