The content discusses a program, P, that can determine whether infinite looping behavior will occur when fed suitable data. If looping is detected, P prints ‘Bad!’ indicating a problem, and if not, it prints ‘Good.’ However, a procedure, Q, is introduced that causes logical paradox by using P’s predictions. Q asks P how A will behave, and if P says ‘Bad!’, Q stops, creating a loop. This ultimately leads to the conclusion that there cannot be a procedure like P that predicts computing machine actions accurately. The content cleverly illustrates the limitations of predicting computer behaviors and the need for users to find their own bugs.
http://www.lel.ed.ac.uk/~gpullum/loopsnoop.html