impermissible usage of "cannot" usually has to do with "refusal of permission"
(sense 4), to which "may not" is preferred. My concern is for liberty.
"Volition," the most beautiful word in any language,
means the act of willing, choosing, or deciding. Men and women have died
for it. Name any other possession more valuable, any other gift more dear.
Surely no person would willingly trade volition for compulsion!
Yet, every day you hear people doing exactly that. Unthinkingly, they renounce
their own free will by saying things like...
Sure, it's just a figure of speech, but notice what happens
if you replace each "can't" with a "won't." Suddenly, you reclaim your
choices, you reassert your will, you have decided.
"I can't sit through this movie."
"I can't eat asparagus."
"I can't stand that music."
Sometimes "don't" works better. Seems like we should say,
"I don't afford another magazine subscription." Funny, though, the English
Language doesn't give us "don't" in front of "afford" (others do).
So, do you want to know when I use "can't"?
Only when I can honestly add "even if my life depended on
it." Accordingly, you may as well know...
Otherwise, I say "don't" or "won't." In addition to asserting
my free will, the conscious effort serves to remind me of a cardinal principle:
"I can't play Beethoven."
"I can't slam-dunk anymore."
"I can't play chess blindfolded."
"I can't strike a match on an ice-cube."
The real choices we have in life are negative (hence
By the way, sometimes I say "I don't play Beethoven."
You can't always have the exact job/house/car/spouse you
want, but you can always turn down any offer or proposal you receive.
A vegetarian relinquishes meat for a purpose.
A bicyclist renounces automobiles to make a statement.
A protester yields up freedom for a cause (an act made especially
poignant when the cause is freedom).