Seeing double time
If you’ve ever jogged in very dim light then maybe you know what I mean when I say that the “frame rate” of my eyesight seems to drop from that of a movie to that of a rapid-fire slide show. It’s as though my eye reduces its shutter speed in order to correct the exposure of images that usually appear to me in Technicolor at 24 frames per second. Another way to put it is that an analog signal (the scene before my eyes) is being digitized (a series of retinal snapshots of the scene) for interpretation by my visual cortex.
A larger question raised by this phenomenon—namely, whether visual perception in particular, and consciousness in general, is a continuous “stream” or only an illusion like that of a child’s flipbook—has been the subject of scientific inquiry and speculation for perhaps as long as two thousand years. Only now does science have the means to find an answer.
While giving blood today I read a mesmerizing little article on vision and consciousness by physician Oliver Sacks in the latest New York Review of Books. (You may know Sacks as the author of Awakenings, a work of nonfiction that was made into a feature film starring Robert De Niro and Robin Williams.) Apparently my intuition about human vision resembling cinematography has some basis in fact. Never mind that Sacks can’t seem to make up his mind whether his conclusions pertain only to vision or to consciousness as a whole.
If, indeed, our eyes enjoy only a flickering motion picture and we do not drink of reality in long drafts then we are a bit like the poor cave-dwellers in Plato’s allegory who perceive only shadows on the wall. Thankfully, this problem is temporary for those who long for Christ’s second Advent.
“For now we see in a mirror dimly, but then face to face. Now I know in part; then I shall know fully, even as I have been fully known.” (1Co 13:12) 
