Where Terence Penelhum sees a deep continuity between John Locke's theory of ideas and David Hume's theory of perceptions, I argue that the two philosophers disagree over some fundamental issues in the philosophy of mind. While Locke treats ideas as imagistic objects that we recognize as such by a special kind of inner consciousness, Hume thinks that we do not normally recognize the imagistic content of our perceptions, and instead unselfconsciously take ourselves to sense a shared public world. My disagreement (...) with Penelhum over Hume's debt to Locke helps to explain our disagreement over the nature of Hume's scepticism. (shrink)