But it is not just that if an impression is copied we get, on Hume’s account, an idea not a belief, it would be redundant even to appeal to the idea where a perceptual belief is concerned. There is just no need on Hume’s account to check the impression before us against our idea of it to ensure that we have identified it correctly. For Hume insists that impressions are self-authenticating and hence that all possibility of mistake is excluded. He writes (1.4.2:7): ‘Since all actions and sensations of the mind are known to us by consciousness, they must necessarily appear in every particular what they are, and be what they appear’. But it would seem to be essential to belief that it is not self-authenticating. (It is for instance precisely because mistake makes no sense with first person expressions of pain that we do not normally say of a person in pain that she only believes she is in pain.) We could put it this way: Humean beliefs by striking upon us with the force of impressions stand in the way of their own truth. They have become opaque when they needed to retain the transparency of ideas.