system
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human
[WH40K] How do the Farsight enclaves resist the influence of the Ethereals?

The Ethereal caste is said to command an unquestioning loyalty from their fellow Tau. To most Tau, following the orders of an Ethereal is as easy and natural as breathing, and they would have a hard time even imagining the concept of saying no to an Ethereal.

So how is that Farsight, and his enclaves, can remain opposed to the greater Tau Empire? Why are the Ethereals incapable of bringing them back into line through diplomacy alone?
gpt
The answer will ultimately lie in HOW the Ethereals maintain control. Early speculation was that it was psychic in nature, but that has long since been almost entirely discounted. The Tau have such an extremely minor psychic signature that any measure of telepathic control would be almost impossible, and studied Ethereal specimens have shown no deviation from the norm in that regard. 

Another proposed explanation is the use of pheromone control. This is based on an obscure reference in Xenology, but should be taken as questionable due to some of the other content of that text, and the fact that it was pure (and at the time untested) speculation of an already somewhat unstable Magos. 

The most likely explanation is that the influence of the Etherials is socially ingrained. It's not natural, but rather cultural. This importance is constantly reinforced in Tau society, particularly through the Caste system, not through the authoritarian oppression of the Imperium, but rather to coercive reassurance and congratulatory praise of contribution. 

Individuals are rewarded for contributing to the Empire via the means their Caste lays out, encouraging them to respect the specialised contributions of other Castes. Earth Caste don't try to fight, because they respect the Fire Caste's superiority in that field, just as the Fire don't try to manufacture weapons. The Ethereals are the recognised leadership Caste, and all others accept their leadership out of a socially conditioned mentality that they are the best equipped to do so. 

The Farsight Enclaves, however, lost their Ethereals at some point during O'Shovah's campaigns. Free from the leadership of an Ethereal, or the resources of the Earth Caste, the Fire Warriors of the Farsight expedition were forced to do something that no other Tau has. Step outside their socially defined boundries. Fire Caste were suddenly expected both to step into a leadership and decision making role (beyond simple military command) as well as maintain their own equipment and facilities. This led to a deep  philosophical rift between the Farsight Enclaves, and the Tau Empire proper, because it compromised the established structure of the Castes. This is also the root of the Farsight belief that the Tau are able to stand on their own, and that they don't need any other races. If the Tau can adapt to any situation, even without the Ethereals, what do they need vassal species for?