re: #422 Pythagoras

Stratagem XVIII (Schopenhauer, The Art of Controversy)

If you observe that your opponent has taken up a line of argument which will end in your defeat, you must not allow him to carry it to its conclusion, but interrupt the course of the dispute in time, or break it off altogether, or lead him away from the subject, and bring him to others. In short, you must effect the trick which will be noticed later on, the mutatio controversiae.