Sentence:  Writing to his colleague George Herbert Palmer - `` Glorious old Palmer '' , as he addresses him - James says that if only the students at Harvard could really understand Royce , Santayana , Palmer , and himself and see that their varying systems are `` so many religions , ways of fronting life , and worth <WSD>fighting</WSD> for '' , then Harvard would have a genuine philosophic universe . 
Meaning of the word marked with <WSD> tags:  exert oneself continuously, vigorously, or obtrusively to gain an end or engage in a crusade for a certain cause or person; be an advocate for