“But surely I recognize a memory image as a memory image, an image of a day dream as an image of a day dream, etc.” ‒ ‒ Remember that you are sometimes doubtful whether you actually saw a certain event happening or whether you dreamt it, or just had heard of it and imagined it vividly. But apart from that, what do you mean by “recognizing an image as a memory image”? I agree that (at least in most cases) while an image is before your mind's eye you are not in a state of doubt as to whether it is a memory image, etc. Also, if asked whether your image was a memory image, you would (in most cases) answer the question without hesitation. Now what if I asked you, “When do you know what sort of an image it is?”? Do you call knowing what sort of image it is not being in a state of doubt, not wondering about it? Does introspection make you see a state or activity of mind which you would call knowing that the image was a memory image, and which takes place while the image is before your mind? ‒ ‒ Further, if you answer the question, what sort of image it was you had, do you do so by, as it were, looking at the image and discovering a certain characteristic in it? (as though you had been asked by whom a picture was painted, looked at it, recognized the style, and said it was a Rembrandt.)