I think GP means that the justification of JTB by definition is recursive and thus has no real foundation. To call something 'true' is to know it is 'true'. I

I think GP means that the justification of JTB by definition is recursive and thus has no real foundation. To call something 'true' is to know it is 'true'. If we are bothering to debate whether knowledge is possible, JTB is unconvincing.