Just because a person is blind doesn’t mean they don’t have a sense of the physical world. They still have the sense of touch, and a sense of what three-dimensional objects are like, even if they can’t see them.
I have had several friends who were blind, including a couple for which I have boundless admiration. My first blind friend was a little girl about seven or eight that I knew when I was about twelve. I remember going to a parade with her. I tried to give a running commentary, and I remember that as an equestrian group was going by, she asked me, “What color are the horses?” She was blind since birth, and I have always wondered what her idea of colors was. How did it affect her when I told her the horses were black?