No matter how much people describe salt to you, you do not know what the experience is really like until you experience it personally. Suppose you were all alone and you came across a bag of very salty potato chips in an unlabeled bag. When you eat the chips, you would experience the taste of salt for the first time, but you would not know that that is what you are experiencing, because you would no other previous experiences or connections with it. Similarly, people blind since birth have no experience of connecting visual sensations with external objects in the real world, or relating them to what sighted people describe as vision.

Therefore, asking them about it is not useful. Do blind people dream in visual images?