In 1762, Bishop Robert Lowth did a grave disservice to the English language when he published his Short Introduction to English Grammar. Rather than basing his grammatical rules in the usage of the best educated speakers and writers of English, he arbitrarily chose to base them on the Latin grammatical system. The result is that many modern usages in English, particularly an alarming number of rules of normative usage and Standard Written English, are based upon those false origins. Lowth's defense of Latin as an "educated" role model for English has given rise to a school of prescriptive grammarians who find it their sworn duty to prescribe this Latinate usage system to those speakers who have managed to escape its inoculation in the educational institutions of English-speaking countries. Prescriptive grammarians are adamant, and their forceful prescriptions and high-brow judgments are irresponsible, and a denial of the rich cultural heritage of our language.

In Lowth's grammar infinitives cannot be split. It is not possible for Lowth because it is not possible in Latin to split an infinitive. Well, of course not. In Latin, an infinitive is one word. However, it is not in English. English infinitives are two words, such as "to split," and there is little logic to keeping them fused together, except that it cannot be done in Latin and Bishop Lowth decided, quite on his own, that English should emulate Latin, and the world followed suit. Thus, one foolish man has made a messy mockery of the rich and dynamic English language.

From Steven Pinker's The Language Instinct:

Forcing modern speakers of English to not - whoops, not to split an infinitive because it isn't done in Latin makes about as much sense as forcing modern inhabitants of England to wear laurels and togas. Julius Caesar could not have split an infinitive if he had wanted to. In Latin the infinitive is a single word like facere or dicere, a syntactic atom. English is a different kind of language. It is an "isolating" language, building sentences around many simple words instead of a few complicated ones. the infinitive is composed of two words - a complementizer, to, and a verb, like go. Words, by definition, are rearrangeable units, and there is no conceivable reason why an adverb should not come between them:

Space - the final frontier . . . These are the voyages of the starship Enterprise. Its five-year mission: to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before.

To go boldly where no man has gone before? Beam me up, Scotty; there's no intelligent life down here. As for outlawing sentences that end with a preposition (impossible in Latin for good reasons having to do with its case-marking system, reasons that are irrelevant in case-poor English) - as Winston Churchill would have said, it is a rule up with which we should not put.