the term aporia It derives from the greek and, literally, means an impassable road. In Philosophy, and in particular in philosophy Socratica, identifies, in the solution of a problem, those arguments that led to two reasonable conditions, but among them incompatible. Plato, in his dialogues, shows how discussions Socrates often they would end identifying aporia.
Socrates with his usual question, What is it? (You're), He aimed in the dialectical process, or to get to a conclusion that it was the only or the finding that the speech would close aporia.
The identification of aporias was used by Socrates, also to provide a reductio ad absurdum. Assuming that the conditions indicated by him were not true, showed that, in that case, The argument ended with the aporia, and then, its premises were necessarily true.