 Unfortunately for this style of explanation of presupposition strengthening, plausibility appears to have its limits. Consider the two examples in (40a,b). If we assume that a cleft "it is X that Y-ed" presupposes an existential, roughly "someone/something Y-ed" then in a dynamic theory of presupposition (40b) will generate the same conditionalized presupposition as results from (40a), which involves the factive "knows", namely the conditional in (40c). However, there is a clear difference in the inferences we would tend to draw from utterances of (40a) and (40b). Whereas (40a) licenses an inference only to the conditional presupposition in (40c), example (40b) leads to the stronger, unconditionalized presupposition in (40d). Under the assumptions we have made, namely that (40a) and (40b) generate exactly the same underlying conditionalized presupposition, the plausibility approach used in Beaver’s framework fails to predict a difference in what is accommodated in these cases.