Ism
Principle, Doctrine
noun, suffix
The main cause behind someone's righteousness is usually what isms, principles or doctrines they believe in. Buddhism, Shintoism, socialism, communism, you name it. If you believe in one of those it's the main driving factor behind what you believe righteousness to be.
しゅぎ
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
フグは肉を食べないよ。菜食主義者だからさ。
Fugu doesn’t eat meat. He’s a vegetarian.