Does perception exist outside of our own nervous system? Philosopher Alva Noë thinks so. We can visualize the back of a tomato, even if our eyes cannot see it. We aren’t offended by profane statements written in a language we aren’t fluent in. This is because our perception is based on more than our five senses; it relies on experience and context as well. 

Alva Noë unpacks this puzzle with a few examples, from being able to visualize things we are not looking at, to a phenomenon called “change blindness.” 

Ultimately, this information can be used to challenge our original understanding of perception, and can expand on the idea that the way one person assesses an object may not precisely match the assessment of another.

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, my, 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 moreover, 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, in what 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 a 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 in placed in an environment. The world is there, and 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. Our ability to experience more than is, in some sense, there and also less than is, in some sense, there, I think, in a very strong way, point us to the fact that what shows up for us, is not so much a matter of what is happening inside of us, but how we are achieving, or failing to achieve, access to what's going on around us.