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In Dune, the Atreides family disregarded any evidence of Dr. Yueh being a traitor since he had been certified by Imperial Suk conditioning. This conditioning apparently ensured loyalty to the Emperor and/or their assigned master, although no details are given regarding how it works. The novel repeatedly mentions that Suk conditioning is unbreakable, with Yueh's inner monologue hinting at some sort of mental triggers or hypnotism.
However, as we see in the novel, all it takes for the Harkonnens to break Yueh is to
torture his wife in a pain amplifier.
Given the seeming ease with which this "conditioning" was broken, why is it considered such an infallible stamp of trust?
Note: I am not trying to find the specifics of how the conditioning is done. What I'm trying to ask is why such conditioning is so highly regarded. If torturing a loved one is all it takes to break an initiate of the program - and that seems to be the case for Yueh - it would be useless.