They say that sight is the primary human sense. I'm not so sure I agree.
In a sense we live in a box made of our senses. Reality is not as we see it (or hear, touch, smell, taste it), we see it as we see it. Reality is not directly apprehended. The information reported by our senses is.
In the Buddhist scheme, the 6th sense is that of thought and mind. Thoughts occur and are sense by mind, or perhaps brain. In the same way that what we see is simply a subsection of input funneled through the "gate" of the eyes and optic nerve, what we think is likewise a subsection of input funneled through the "gate" of our brain and conditioning.
One of the sharp distinctions between something seen, and something thought, seems to be that something seen lies outside of our boundaries and can be tied with the source of other sensory impressions. We can see the dog, hear it barking, smell it's fur, taste it's drool, feel it's warmth. We also have thoughts about the dog, but they seem to float in some other "spaceless space" behind the eyes and between the ears.
Since thoughts are not so easily tied to objects, and since they are so fluid (we might like dogs in general, but not that one in particular, or not as much as we did yesterday, etc.) they seem to occupy some mysterious special case.
Perhaps this explains part of the mechanism of self-identity. Just as thoughts about a dog can be so tenuous, chimeric, and mysterious, how much more so are they about something we can't even see? The story running in the brain that we call our selves. Could it be that, that very mystery itself is what keeps it so potent? If that story were something we could also touch, smell, see, taste, and hear, would we give it so much weight?
What do you think?