Given a list followed by an independent clause, should the list be set off with a colon? For example, "Pie, cake, cookies: all are critical to happiness in this lonely world." Should this be a semicolon instead?
Definitely a colon is not correct in such position. It could be used before the list not after it. A better sentence could be for example:
The critical things to happines in this lonely world are: pie, cake and cookies.
I am not sure what I would use in the original sentence. Maybe a semicolon would be good.