Many English speakers cannot understand basic grammar
"Of course some people are more literate, with a larger vocabulary and greater exposure to highly complex literary constructions. Nevertheless, at a fundamental level, everyone in a linguistic community is supposed to share the same core grammar, in the same way that given normal development we can all walk."
The supposition that everyone in a linguistic community shares the same grammar is a central tenet of Noam Chomsky's theory of universal grammar.
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Research showing that people not only are not aware of the grammar, but in fact can't understand it or use it.
