Can You See the Insides of Your Eyelids?
Visitors to The Splintered Mind in August and September will know I have this weird fascination with the question of what we see with our eyes closed. Admittedly, maybe the issue is not quite as important as the nature and pursuit of happiness, which I wrote about Friday.
Setting aside issues about afterimages, "light chaos", visual imagery, etc., here's one possibility: we see the insides of our eyelids. What do you think?
If I close one eye and hold one hand about a foot before the other eye, it's clear that I see my hand, right? Now I bring it slowly closer to the open eye until it eventually covers it completely, blocking out all light (though my eye remains open). Is there a point at which I go from seeing the hand to not seeing the hand? Or, as I sit here hand over eye am I see seeing the hand, though no light whatsoever is reflecting off it or coming into my eye?
It seems to me slightly more natural to say that I see "nothing" than to say that I still see my hand. Maybe, then, we can say that when the hand stops reflecting light into my eye I stop seeing it? But reflecting light into the eye is a strange criterion for seeing, since it implies that I could never see anything that was absolutely black. And we don't want to say that: A good enough coat of black paint doesn't make things invisible -- just very black!
Maybe we can say that I see things as long as they would reflect light shining on them, into my eye, if they were not completely light-absorbent? No, that doesn't work either: Translucent things are visible, so reflecting light into my eye can't be a condition of seeing. And, indeed, my hand is partly translucent, as can be seen if I shine a flashlight through it, while sitting in the dark.
So say I do sit in the dark with a hand completely over an open eye and shine a light through that hand into the eye. Now am I seeing the hand? -- the redness of its blood, say? Or am I just seeing the light? Or both? And if I do see the hand in this case, do I also see it in the case when there is no detectable light coming through? Maybe we should say this, at least: I can see that something (mostly) opaque is covering my eye, even if I can't see the object itself?
All the same questions arise, of course, in the more normal case where one's eyelids are doing the occluding rather than one's hand.
What a magnificent tangle!