Imagine this lady and her unicorn. Furnish them with lots of visual detail. How big are they? How would they look from another angle? Put in some non-visual detail. Suppose our lady gave the little thing a good smack. What sound would it make? Suppose it chewed on some clover-like leaves: How would that sound? How would it smell? Does her perfume overwhelm the clover?
You are entertaining a sensory image. Much of our mental life is directed towards sensory images. Yet it is not well understood how and what they signify. I’ll pose three fundamental questions about imaging that bear on central issues in the philosophy of mind. It may seem obvious how they should be answered—but they mask the potential for sharp disagreement.
- Can your image of the unicorn be true?
- Your image is as of a brown unicorn. Is it, similarly, of an existent one?
- Are you (necessarily) imagining yourself observing the lady and her unicorn?
Charles Siewert gives us both sides of this question. On the one hand, “if you merely freely fantasize a house, well, there is no particular of which we can say: you accurately visualized that.” Since you freely fantasized the unicorn, the same holds: even if you came across an animal that exactly matched your image, your image was not about this animal, and can’t therefore be an accurate or true visualization of it. It isn’t true in virtue of the fact that there happened to be something just like what you imagined.
Siewert hesitates, however. If I came upon an actual unicorn, I might exclaim: “It’s just as I imagined it.” So asks Siewert: “Mightn’t this be a case where there was something I accurately visualized?” (Notice, though, how the question changes: to say that there is something I accurately visualized is different from saying that I actually visualize this.)
If images can't be true, what does this say about sensory content?
2. Hume’s answer concerning existence is famous (though some attribute it to Kant). We can separate the brownness idea from the unicorn idea: that is, we can imagine a non-brown unicorn of the same shape. If existence were like this, we should be able to detach it as well. But there is nothing we can similarly detach or modify that would make the image be of a non-existent unicorn. So “the idea of existence is the very same with the idea of what we conceive to be existent.”
Hume’s argument proves too much. When we remember something (imagistically), we image it as past. When we enjoy perceptual experience of the same thing, we experience it as present. But the image stays the same—no part of the remembered image is modified to indicate pastness. This should lead Hume to say “the idea of present existence is the very same with the idea of what we conceive to be presently existent.” This seems absurd: we do not imagine everything we imagine as presently existent.
This marks a problem not discussed in the literature. What is it about imagistic memory that marks it as of the past?
3. Are you a part of what you image? You might think that since there is ‘left’ and ‘right’ in images, there must be also be a “me” that indexes these directions. For you to image something to the left is to image it as to the left of you. Therefore, you must be an element in all of your imagings.
Is this true? Your beloved calls you on the phone, and describes the bay in front of her, with a mountain to the left and a beach to the right. You visualize it: "How lucky you are darling, to be there."
Are you visualizing yourself looking at it? No: you are simply trying to visualize how it looks. Not how it looks to her, nor to you if you were there. Just how it looks. This is why John Campbell writes: “the egocentric frame employs monadic spatial notions such as ‘to the right’, ‘to the left’ . . . and so on rather than relational notions, such as ‘to my right’” and so on.
The question bears on the objectivity of appearance, and, as such, it impinges on the conceivability/possibility question Jon Cogburn referenced a little while ago. You might think that what makes perceptual experience accurate or inaccurate is its indexical quality: this is how things are from where I stand now. Images, on the other hand, are unindexed. They are just about how things appear—how they appear to anybody. Images represent objective appearance—an idea suggested by work of Susanna Schellenberg.
If images are of objective appearance, you should not be able to image impossible scenes (such as the Penrose staircase beloved of M. C. Escher)?
If appearances are objective, you should be able to imagine a scene as so, only if there is a scene that could appear so. Can you imagine a Penrose staircase? Here's another terrific visualization:
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