Sententialism is the view that intensional positions in natural languages occur within clausal complements only. According to proponents of this view, intensional transitive verbs such as ‘want’, ‘seek’ or ‘resemble’ are actually propositional attitude verbs in disguise. I argue that ‘conceive’ (and a few other verbs) cannot fit this mould: conceiving-of is not reducible to conceiving-that. I offer a new diagnosis of where Berkeley's ‘master argument’ goes astray, analysing what is odd about saying that Hylas conceives a tree which is not conceived. A sententialist semantics cannot account for the absurdity in attitude ascriptions of this type: we need to acknowledge irreducibly non-propositional (but none the less de dicto) conceiving.