preposition ending a sentence. It was John Dryden, the 17th-century poet and dramatist, who first promulgated the doctrine that a preposition may not be used at the end a sentence. Grammarians in the 18th century refined the doctrine, and the rule has since become one of the most venerated maxims of schoolroom grammar. But sentences ending with prepositions can be found in the works of most of the great writers since the Renaissance. In fact, English syntax not only allows but sometimes even requires final placement of the preposition, as in We have much to be thankful for or That depends on what you believe in. Efforts to rewrite such sentences to place the preposition elsewhere can have comical results, as Winston Churchill demonstrated when he objected to the doctrine by saying “This is the sort of English up with which I cannot put.”
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Even sticklers for the traditional rule can have no grounds for criticizing sentences such as I don’t know where she will end up or It’s the most curious book I’ve ever run across; in these examples, up and across are adverbs, not prepositions. You can be sure of this because it is impossible to transform these examples into sentences with prepositional phrases. It is simply not grammatical English to say I don’t know up where she will end and It’s the most curious book across which I have ever run.
