This is a thought experiment intended to get you in the mind of someone who has been disabled from birth (this idea was spawned by thinking about someone who is deaf).
Imagine that tomorrow you're going about your daily life and you notice that people start treating you a bit differently. You don't really know why, things seem the same to you. You ask one of your friends and they say that you're "abrent" [I've made up a word here]: i.e. you're missing a sense that everyone else seems to have. Apparently it's something around you that you interact with all the time, but you can't perceive it. People try to describe it to you but obviously and utterly fail because how do you describe an entirely subjective experience?
Now imagine how someone might feel who is deaf from birth. As they grow up, they can obviously see people communicate imperceptibly with others. It seems that someone opens their mouth and moves it around and the other person knows exactly what they're communicating. Someone tries to explain that they're making sounds with their mouth that the other person hears, but how do you explain sound? How would you explain color to a blind man? If this person were somehow excluded from all other humans, they might think they were a perfectly normal human being. But put them in a society of hearing humans and they're labeled "deaf" and it's claimed that there is a sense that they are missing.
How would you feel if you found out tomorrow that there is a "sixth-sense" that you've been missing out on this whole time? I can just imagine the situation now:
[You and a friend walk outside]
Friend: Oh, it's going to rain today!
You: Wait, how do you know?
Friend [looks at you dumbfounded]: Because my fingertips tingle, obviously.
You: What do you mean your 'fingertips tingle'?
Friend: Wait, you don't feel that? Everyone feels that.
You: What do you mean 'everyone feels that'?
Friend: Like...hey, John, do your fingertips tingle?
John: Yeah. That's what they're supposed to do. It means it's going to rain. [Walks off confused]
Friend: Mary, are your fingertips tingling?
Mary [gives a weird look]: What is this, a trick? Obviously they are.
Friend [turns back to you]: See?
You: Huh. Well I just don't feel it. What's it supposed to feel like?
Friend: It's kinda like you touched an electric fence, but not quite. Almost....cold? Uh, it's kinda hard to explain.
Imagine how your life would change from there on out.
