 which is read as “if \(\varphi\) is the case, then there is a formula \(\psi\) after whose announcement \(\varphi\) will be  known”.[19]  This reading of the verificationist thesis brings us in touch with a number of results in dynamic epistemic logic on unsuccessful formulas (those that become false after being truthfully announced; van Ditmarsch &amp; Kooi 2006; van Benthem 2011; Holliday &amp; Icard 2010), which indicate that indeed not all sentences are learnable. In fact, this solution shows us that