 Notice that T-knowability is free of the paradoxes that we have discussed. It is free of Fitch’s paradox and the related  undecidedness paradox.  For both results substitute the problematic Fitch conjunction, \(p \wedge \neg Kp\), for the variable in \(p \rightarrow \Diamond Kp\), giving us \((p \wedge \neg Kp) \rightarrow \Diamond K(p \wedge \neg Kp)\). That is, they require that \(p \wedge \neg Kp\) be knowable if true (line 2 of Fitch’s result). But \(p \wedge \neg Kp\) is not Cartesian, since \(K(p \wedge \neg Kp)\) is provably inconsistent (entailing the contradiction at line 6 of Fitch’s result). In effect, TKP offers the most tolerant restriction needed to prohibit the bothersome substitution. For it only prohibits substituting those statements for which it is logically impossible to know. 