It's in fact a different sort of word-meaning as might prevail on some planet where all the gods were only made up; it means not 'belief without evidence' but rather 'whatever sort of emotional relationship a cleric of a god typically has to that god, which facilitates their choosing and their continued clerichood, as is usually also held by that god's lay worshippers'.
"My faith is my belief that Hell will hurt me very badly, in my afterlife, if I slack off; and that Asmodeus will abandon me and leave me powerless, if I cease to serve Him. Previously my faith was also upheld by the temporal rewards of being an Asmodean 6th-circle, and by expecting my Church to hunt me down, torture me for a few weeks, and kill me, if I tried to leave the Church. But those aspects of my faith are weakened on this planet -- though not at all severed; Aspexia Rugatonn could still show up with a Gate." Possibly that is why Asmodeus has felt more distant it would speak ill of Esta if his faith were that fragile and therefore this cannot be the case. "Those are the primary tenets of my faith, what dath ilan would call the crux; but it does not hurt that I can see the rightness of a universe in which incompetence is punished by pain, and more competent people get to command the less competent."