1. In contemporary logic an argument that negatively refocuses concern on the character of one’s interlocutor, distracting from the subject matter under discussion.  Such an argument is regularly considered a fallacy in demonstrative logic.  It does, however, represent a kind of attenuated form of a rhetorical argument from either ethos (focusing on the supposedly negative character of someone holding a position) or pathos (focusing on the passionate reaction had by listeners faced with the account of this person’s supposed character).  2. In classical logic, an ad hominem argument was contrasted to an argument ad rem.  In an ad hominem argument, the terms of the discussion are conceded to one’s interlocutor.  In such an argument, one would seek to show, at the very least, that the interlocutor’s purported conclusion does not hold true.