Everything that you see is your minds eye. What you call reality is your brains interpretation of input from the retina. You never see the external world but only your brains interpretation of it. The room you are sitting in right now exists inside of your brain. Everything you know see, smell, taste touch, these are all created by your brain. Normally in normal mind states we assume that these interpretations correlate with some external physical world. On hallucinogens or electrical stimulation of the brain we can create new experiences that do not correlate with any information in the "external physical world." You are right that it is hard to describe the experience but never the less we can use some linguistic symbols to explain some of the experience such as squares, or colors, arebesque patterns, faces. One who is born blind has never learned to connect the linguistic symbols with the visual experiences (as they have none). Thus they would NOT be able to describe what they are seeing as they have no words to describe it. People with vision at least can attempt to explain the experience and there is no question that certain visual images represent shapoes, aliens, eleves... these visual experiences we have learned through our culture to associate with linguistic symbols. One who has never seen could not possibly all of a sudden know what an elf or an alien looks like or even a color one needs visual experience to learn these associations. Additionally the visual system requires sensory input to form and function properly. Thus it is very unlikely that an individual born blind would see the same imagery that an normal subject would. As there brain simply is not wired in this way and thus it is virtually impossible. That is not to say that they wouldn't see anything but it would certainly not be as complex as one with vision. Think about it a color is a completely subjective experience. Someone born blind takes a hallucinogen and suddenly sees a color he has no word for that experience in fact he wouldn't even be able to categorize it as even belonging to the linguistic concept called a color. It may be possible to teach him some symbols (not a color)however even this would be difficult because there is no way for us to know what he is seeing and as he would have trouble explaining it. Maybe through art although it would be quite difficult for a blind person to draw. Meaning if they drew a face we could tell them that is a face.