Alva Noë: Consider this: we are conscious of both more and less than affects our nervous system. Let me give you an example. I look at a tomato. It’s sitting there on the counter in front of me. It’s red and bulgy and three dimensional and I experience all that. I experience all that visually. I have a sense even visually of the back of the tomato, not that I can see the back of the tomato. It’s out of view and yet it’s part of my experience of the tomato that it has a back. It’s present in that sense to me, but note it doesn’t strike my retina. It’s present. It informs. It structures my visual experience without actually being an element that stimulates my nervous system or consider I look at writing on a text--or a better example is I walk into a room and there's graffiti on the wall and imagine it’s graffiti that I find really offensive. I walk in. I look at it. I flush. My heart starts to race. I‘m outraged. I'm taken aback. Of course if I didn’t know the language in which it was written I could have had exactly the same retinal events and the same events in my early visual system without any corresponding reaction.
So it’s an interesting puzzle. Much more shows up for us than just what projects into our nervous system. In fact, however, paradoxical it sounds if we think of what is visible as just what projects to the eyes we see much more than is visible and more over, just because something does enter our eyes, provide a stimulus to the nervous system that doesn’t mean we experience it. Psychologists have shown this in the laboratory with experiments that would have been called change blindness. You can be looking at something and as you’re looking at it it’s changing and under quite normal conditions people will to a surprisingly large degree fail to be able to describe or notice that a change has occurred. It’s a little bit like if I have a plate of French fries and you say to me, "Hey, what’s that over there behind your shoulder," and I go like this and you take one of my fries and when I turn around I probably won’t notice that anything is missing. I didn’t have that kind of detailed internal representation of the plate such that I can compare how the plate looked before I turned away and how it looked when I turned back and notice a discrepancy, but that’s how our experience is in general. We find ourselves emplaced in an environment. The world is there. We don’t need a detailed internal representation because we can move our heads, flick our eyes, redirect our interest and get the information we need as we need it.