I can't read Chinese. I also can't use sunlight, water and carbon dioxide to photosynthesize starch. (Although I admit that would be very cool.)
These are two very different uses of the word "can't." Photosynthesis is pretty much an absolute; my cells just plain lack the machinery to do it, and barring some pretty amazing technology for modifying living cells, it will always be beyond my ability. Reading Chinese is a different kind of "can't." What I really mean is that right now I can't. I don't know how.
What we've uncovered is the difference between "ability" and "skill."
A skill--like reading Chinese--can be developed by anyone who is motivated (and in this particular example, let's also stipulate "not blind.") A biological ability like photosynthesis is something that is dictated by nature; no matter how motivated, I cannot learn to photosynthesize. It is sensible to say that I "can't" photosynthesize. But it is not sensible to say I "can't" read Chinese. What I should be saying is "right now I can't read Chinese." If I never intend to learn, I might say "I don't know how to read Chinese." If I were in the process of trying to learn, I might say "I can only read a few characters" or "I can read Chinese at an intermediate level" or even "I'm not ready for the kind of stuff I want to be able to read." Those are accurate statements. They reflect either current time (not yet); current level of skill (only a little, intermediate level); or gap between current skill and desired skill. When we're talking about skill, let's face it: almost any human can acquire almost any skill, to some degree. If there are physical or cognitive limitations involved, the desired level of skill may not be attainable: I can shoot baskets but am too short to slam dunk; I can learn a foreign language but at my age will probably always have an accent. But some level of skill is always possible. From that we can conclude an uncomfortable truth:
"I can't" is almost always a lie. Because rarely does anyone ask us to do the humanly impossible (like photosynthesize).
The truth about skill (i.e. the truth most of the time) is "I don't know how...but I could learn...!"
