Q: You mentioned in passing on WNYC that the prohibition against splitting an infinitive is not a legitimate rule. Can you explain? I’ve always heard otherwise.
A: The belief that it’s wrong to split an infinitive is a notorious myth. Grammarians have been trying to debunk it for generations. This never was a rule. It was merely a misconception based on the wrong-headed notion that English (a Germanic language) should conform to the rules of Latin (a Romance language).
An infinitive is a verb in its simplest form and usually has the word “to” in front of it: “Darcy helped to find Lydia and Wickham.” But the “to” isn’t actually part of the infinitive and it isn’t always necessary: “Darcy helped find Lydia and Wickham.”
The myth against “splitting” an infinitive, which I discuss in my book Woe Is I, was born in the 19th century when Latin scholars misguidedly called it a crime to put a descriptive word between the prepositional marker “to” and the infinitive: “Darcy helped to quickly find Lydia and Wickham.”
Since “to” isn’t part of the infinitive, however, there’s nothing to split and the whole idea of “splitting” an infinitive is nonsense. (In Latin, the infinitive is a single word without a prepositional marker, and obviously can’t be split.)
A sentence often sounds better when the “to” is close to the infinitive, but there’s no harm in separating them by putting an adverb or two in between. Writers of English have been happily “splitting” infinitives since the 1300s. So, if you want to happily join them, feel free. For more about the so-called split infinitive and other misconceptions, go to the Grammar Myths page of Grammarphobia.com.