Why not?
Every exceptional programmer I've ever met was unexceptional at one time. Something happened for them to become exceptional. I personally believe that while that "something" is most often "doing", "training" is often a big part of the equation. And that training is more often than not training their beliefs as much as training their skills.
Many of the best programmers I've even known never imagined themselves being able to do what eventually became their norm. For a lot of them, all it took was the guidance of a caring mentor or trainer to see the possibilities.
Regardless of where programmers come from, I take it as a serious responsibility to help them become what they can be. Not saying "can't" is the first step.