A.N. Prior was a logician during the heyday of ‘ordinary language philosophy’, yet in may ways his view of semantics was very different from that assumed in the model-theoretic accounts which have become influential since the work of Richard Montague In this talk I will look principally at Prior's book ‘Objects of Thought’, in which he sets out his views on the semantics of propositional attitude sentences, and I will concentrate on what appears to be a lack of recognition of the importance of compositionality in a theory of meaning.