What is "aporime"

An aporime is a problem difficult to resolve, and which has never been resolved, though it may not be, in itself, impossible.

The word is derived from the Greek , which signifies something very difficult and impracticable, being formed from the privative α, and , "passage". When a question was proposed to any of the ancient Greek philosophers, especially of the sect of Academists, if he could not give a solution, his answer was , q.d. "I do not conceive it; I cannot see through it; I am not able to clear it up."