Sentence:  This was the phrase of that interesting mystic St. Paul (Saul) of Tarsus ... who did so much to pervert and enlarge the simpler cosmopolitan fraternalism of Jesus of Nazareth ... before it was finally overwhelmed and lost in the sacrificial <WSD>sacerdotalism</WSD> of formal Christianity. 
Meaning of the word marked with <WSD> tags:  The belief that priests can act as mediators between God and mankind.