Sentence:  He was thinking; but the glory of the song, the swell from the great organ, the clustered lights, […], the height and vastness of this noble fane, its antiquity and its strength—all these things seemed to have their part as <WSD>causes</WSD> of the thrilling emotion that accompanied his thoughts. 
Meaning of the word marked with <WSD> tags:  The source of, or reason for, an event or action; that which produces or effects a result.