In The Crucible, how is Danforth a victim of his own logic?
Danforth, in my opinion, is one of the most interesting characters in this excellent play, precisely for the reason that you have suggested in your question. Having so cogently and authoritively "proven" that the people convicted of witchcraft have trafficked with the devil, when Mary Warren brings her charge against Abigail, he leaves himself open to attack from Abigail and the other girls. By giving the girls such power and authority, and using them as the main "proof" of witchery, it seems as if he has placed his head in a noose that it cannot be removed from. Note the way in which Abigail responds to his questions about the veracity of what she has "experienced":
I have been hurt, Mr. Danforth; I have seen my blood runnin' out! I have been near to murdered every day because I done my duty pointing out the Devil's people--and this is my reward? To be mistrusted, denied, questioned like a--
In response to this, Danforth replies in a "weakening" tone, that clearly indicates the way that he is somewhat intimidated himself by Abigail. Abigail, indeed, is so sure of her position that she feels confident enough to suggest that Danforth himself might be open to the charge of witchery.