My Dear, Obsolete, Grice

From:

http://painintheenglish.com/?p=1520

""Therefore" is an adverb. ... Previously, a semicolon before, and a comma after would be required, but this is now considered obsolete. Simply preceding with a comma is sufficient."

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Vis a vis Grice's:

"Jack is an Englishman; he is, therefore, brave."

---- I Kant do witout the semi-colon. A simple comma, even if it is an Oxford one, seems vulgar.