How’s that then? Suppose Gombrich is Hing a NC, it doesn’t follow that anyone who can HaNC can make us see nonexistent thread; perhaps it’s necessary but not sufficient. On the other hand, maybe it is true that anyone who can HaNC can make us see things, but Gombrich is fumbling his needle- it’s just not noticeable because the thread actually exists in that case.
How’s that then? Suppose Gombrich is Hing a NC, it doesn’t follow that anyone who can HaNC can make us see nonexistent thread; perhaps it’s necessary but not sufficient. On the other hand, maybe it is true that anyone who can HaNC can make us see things, but Gombrich is fumbling his needle- it’s just not noticeable because the thread actually exists in that case.