A command of the grammar of one’s native language is typically taken for granted as something a speaker acquires from childhood on through acculturation and education into adolescence and adulthood. The basic rules of grammar are generally taken to be securely embedded in one’s knowledge by around the age of twelve. Naturally, neophyte speakers make mistakes, and the correcting done by parents and teachers eventually remedy such episodic defects so that they are not perpetuated. Some errors that are unattended to may eventually enter the language and change its norms over the language’s history. But at any given stage in a language’s development, the grammatical norms are fundamentally stable and adhered to by a broad population of speakers (and writers) of the standard.
When grammatical norms are violated by adult native speakers, assuming such errors are not merely ‘slips of the tongue’, they ought to be regarded as lapses in competence that betoken, at bottom, not just a lacuna in one’s knowledge but a fundamental failure of thought. Language is not just the outer garment in which knowledge is dressed (expressed) but the very stuff of thought. Hence a failure to adhere to the rules of grammar is not just a contravention of social norms but a sign of wrong thinking no less significant than faulty reasoning or factual inaccuracy.
In the light of such general cognitive considerations, when a native speaker makes, viva voce, a fundamental grammatical error that goes uncorrected––i. e., is not just a lapsus linguae––one is justified in considering this phenomenon as a token of a species of defective knowledge, with all the consequences that such a judgment entails. Here is a contemporaneous example.
In a speech last night (June 30, 2013) to a gathering at the University of Cape Town, South Africa, which was broadcast today on NPR (“Morning Edition”), President Barack Obama, a native speaker of English with both a college and a law degree, is heard uttering the erroneous complement of the verb confer ––viz., saying “confer to” instead of “confer on“––in referring to an honorary degree that had been awarded to Nelson Mandela by the University. This speech (as evidenced by the photos online) was delivered without a text or teleprompter, which means that the grammatical error was produced spontaneously, in context (though probably not ex tempore).
However one regards the current president, latter-day occupants of the office have not routinely distinguished themselves by an exemplary command of their native language (witness George W. Bush), so it is perhaps no surprise to note an occasional linguistic lapse in their public pronouncements. But a mistake in verbal government cannot simply be written off in the way a stylistic infelicity might be because it adverts to a fundamental consideration of the speaker’s competence.