 which poses a problem for the non-omniscient verificationist. The derivation that leads to the paradox as we have stated it here is based on a multi-modal logical system in which at least the following principles hold: (i) the principle of non-contradiction, to capture that contradictions cannot be true and can also not be considered possible, (ii) the classical laws of double negation, transitivity of the material implication and substitution, (iii) normality of the modal logic operator K, the modal logic principle T stating that knowledge is truthful, and the normality of the modal possibility operator \(\Diamond\). The simplest presentation of the paradox which shows how it leads to the unwanted equivalence between truth and knowledge, can be found in van Benthem (2004). Start with the formula stating the verificationist thesis, \(\varphi \to \Diamond K\varphi\), and substitute \(\varphi\) with \((p \land \lnot Kp)\):