Consider Phlebas (Culture, #1)

by Iain M. Banks

That was the way Horza felt about Fwi-Song. He had to treat him as the maniac he obviously was. The fact that his insanity was dressed in religious trappings meant nothing. No doubt the Culture would disagree, claiming that there was ample common ground between insanity and religious belief, but then what else could you expect from the Culture? The Idirans knew better, and Horza, while not agreeing with everything the Idirans stood for, respected their beliefs. Their whole way of life, almost their every thought, was illuminated, guided and governed by their single religion/philosophy: a belief in order, place and a kind of holy rationality. They believed in order because they had seen so much of its opposite,