In his essay "On the Logic of Perception' (1969) Jaakko Hintikka argued that the logic of perceptual terms ("perceive', "see', "hear', etc.) is a branch of his more general theory of propositional attitudes. According to this thesis, perception — just like knowledge, belief, and memory — is a pro-positional attitude in the sense that it involves a relation between a person (the "percipient') and a proposition. Moreover, the syntax and the semantics of expressions of the form "a perceives that p' can be analyzed by means of the possible-worlds semantics essentially in a similar fashion as Hintikka has treated epistemic logic in his classical Knowledge and Belief (1962) and in a series of later papers.¹