It's fairly certain most people believe that without their eyes they cannot see. This is false of course.
Our eyes are intensely complex cameras which present a picture to the visual cortex of our brain, known as the dura. The picture is then interpreted by the brain based on the thousands of images you've collected in your so-far lifetime. If you've never seen a thing and it's being presented to your dura, the brain will have to analize the picture and store the information in your visual cortex. That's the basic process.
It's fascinating how easily our cameras can be fooled. If we see smoke, we may immediately think of fire, a comparative interpretation of our brain, and even "see" flames where there are none. What if we could bypass those cameras and present pictures directly to the dura of another kind, perhaps infra-red images. We'd see things normally invisible to the rods and cones of the retina. Would it be illusional? It depends on the assumtions made by the brain, I'd say.
Some people claim to "see" images around others, ectoplasmic shapes, softly-lighted humanoids that appear to be people connected to that person, i.e. their deceased grandmother, etc. Like Sylvia Browne. Ghosts. She claims to hear and see a person's dead friends and relatives. Assuming she's actually seeing something, she's not using her cameras, her eyes, to see them. Images are being shown to her visual cortex that are not coming from her eyes. Where are they coming from? (Perhaps her brain's interpretation of what is expected of her to see?)
If we could see the invisible world surrounding us, the potential would be limitless. And since we "teach" our brain to see, would this abililty somehow further our continuing evolution?
Little experiment: Find two objects of differing color and shape (like a hair brush and a TV remote) Hold each one in front of each eye, about 15", then look directly ahead of you, staring at the space between. Wait a few seconds and see where your eyes tend to travel. I'll reveal what it means afterward, so I don't prejudice your answer. Try it !