Sentence:  And then they believe him, not for his own authority, but for a truth's sake, which they derive from elsewhere: to what end then should they cite him as <WSD>authentic</WSD> for episcopacy, when they cannot know what is <WSD>authentic</WSD> in him, but by the judgment which they brought with them, and not by any judgment which they might safely learn from him? 
Meaning of the word marked with <WSD> tags:  authoritative