Exactly-- it's not that there is some bright line there, that I'm capable of vector calculus, but not.... well, some way-out-there-esoteric-theoretical mathematics.
But it's probably there somewhere.
Are children with profound mental retardation capable of "learning to read?"
Well, yes, probably SOME of them are, given enough of the idealizing inputs discussed. But not all of them, and it may depend on your standards-- is this at the level of a 3rd grader? A sixth grader?
Can they simply "grow" into this task if they really, really want to, and we all "encourage" them enough?
I'd argue that the answer is "no." That's not to say that life ought to be filled with people saying "Nope, not for you."
Because people are complicated and surprising-- some of them probably CAN, in spite of all the predictive evidence arguing that they shouldn't be capable. This is how people escape from horrifying childhood circumstances and go on to prestigious careers, after all-- instead of prison.
