Allusions - Paradise Lost

"'By what instinct do you pretend to distinguish between a fallen seraph of the abyss and a messenger from the eternal throne - between a guide and seducer?'" (Bronte 200)
 

Here Mr. Rochester is alluding to Paradise Lost by John Milton. Edward is seeing a vision before him of an angel. Jane warns him that the angel "is not a true angel," and that he should be wary of such visions. Mr. Rochester is admitting that he has gone down the path of sin, and is further tempted to it by the devil, the fallen angel himself. It is Jane who realises this, and tells him he should follow the path of righteousness instead, by acts of love rather than selfishness as Rochester has known.