Today is the fiftieth anniversary of the first airing of Star Trek, so I thought it was a good opportunity to talk about split infinitives. (So did Merriam-Webster, which beat me to the punch.) If you’re unfamiliar with split infinitives or have thankfully managed to forget what they are since your high school days, it’s when you put some sort of modifier between the to and the infinitive verb itself—that is, a verb that is not inflected for tense, like be or go—and for many years it was considered verboten.

Kirk’s opening monologue on the show famously featured the split infinitive “to boldly go”, and it’s hard to imagine the phrase working so well without it. “To go boldly” and “boldly to go” both sound terribly clunky, partly because they ruin the rhythm of the phrase. “To BOLDly GO” is a nice iambic bimeter, meaning that it has two metrical feet, each consisting of an unstressed syllable followed by a stressed syllable—duh-DUN duh-DUN. “BOLDly to GO” is a trochee followed by an iamb, meaning that we have a stressed syllable, two unstressed syllables, and then another stressed syllable—DUN-duh duh-DUN. “To GO BOLDly” is the reverse, an iamb followed by a trochee, leading to a stress clash in the middle where the two stresses butt up against each other and then ending on a weaker unstressed syllable. Blech.

But the root of the alleged problem with split infinitives concerns not meter but syntax. The question is where it’s syntactically permissible to put a modifier in a to-infinitive phrase. Normally, an adverb would go just in front of the verb it modifies, as in She boldly goes or He will boldly go. Things were a little different when the verb was an infinitive form preceded by to. In this case the adverb often went in front of the to, not in front of the verb itself.

As Merriam-Webster’s post notes, split infinitives date back at least to the fourteenth century, though they were not as common back then and were often used in different ways than they are today. But they mostly fell out of use in the sixteenth century and then roared back to life in the eighteenth century, only to be condemned by usage commentators in the nineteenth and twentieth centuries. (Incidentally, this illustrates a common pattern of prescriptivist complaints: a new usage arises, or perhaps it has existed for literally millennia, it goes unnoticed for decades or even centuries, someone finally notices it and decides they don’t like it (often because they don’t understand it), and suddenly everyone starts decrying this terrible new thing that’s ruining English.)

It’s not particularly clear, though, why people thought that this particular thing was ruining English. The older boldly to go was replaced by the resurgent to boldly go. It’s often claimed that people objected to split infinitives on the basis of analogy with Latin (Merriam-Webster’s post repeats this claim). In Latin, an infinitive is a single word, like ire, and it can’t be split. Ergo, since you can’t split infinitives in Latin, you shouldn’t be able to split them in English either. The problem with this theory is that there’s no evidence to support it. Here’s the earliest recorded criticism of the split infinitive, according to Wikipedia:

The practice of separating the prefix of the infinitive mode from the verb, by the intervention of an adverb, is not unfrequent among uneducated persons. . . . I am not conscious, that any rule has been heretofore given in relation to this point. . . . The practice, however, of not separating the particle from its verb, is so general and uniform among good authors, and the exceptions are so rare, that the rule which I am about to propose will, I believe, prove to be as accurate as most rules, and may be found beneficial to inexperienced writers. It is this :—The particle, TO, which comes before the verb in the infinitive mode, must not be separated from it by the intervention of an adverb or any other word or phrase; but the adverb should immediately precede the particle, or immediately follow the verb.

No mention of Latin or of the supposed unsplittability of infinitives. In fact, the only real argument is that uneducated people split infinitives, while good authors didn’t. Some modern usage commentators have used this purported Latin origin of the rule as the basis of a straw-man argument: Latin couldn’t split infinitives, but English isn’t Latin, so the rule isn’t valid. Unfortunately, Merriam-Webster’s post does the same thing:

The rule against splitting the infinitive comes, as do many of our more irrational rules, from a desire to more rigidly adhere (or, if you prefer, “to adhere more rigidly”) to the structure of Latin. As in Old English, Latin infinitives are written as single words: there are no split infinitives, because a single word is difficult to split. Some linguistic commenters have pointed out that English isn’t splitting its infinitives, since the word to is not actually a part of the infinitive, but merely an appurtenance of it.

The problem with this argument (aside from the fact that the rule wasn’t based on Latin) is that modern English infinitives—not just Old English infinitives—are only one word too and can’t be split either. The infinitive in to boldly go is just go, and go certainly can’t be split. So this line of argument misses the point: the question isn’t whether the infinitive verb, which is a single word, can be split in half, but whether an adverb can be placed between to and the verb. As Merriam-Webster’s Dictionary of English Usage notes, the term split infinitive is a misnomer, since it’s not really the infinitive but the construction containing an infinitive that’s being split.

But in recent years I’ve seen some people take this terminological argument even further, saying that split infinitives don’t even exist because English infinitives can’t be split. I think this is silly. Of course they exist. It used to be that people would say boldly to go; then they started saying to boldly go instead. It doesn’t matter what you call the phenomenon of moving the adverb so that it’s snug up against the verb—it’s still a phenomenon. As Arnold Zwicky likes to say, “Labels are not definitions.” Just because the name doesn’t accurately describe the phenomenon doesn’t mean it doesn’t exist. We could call this phenomenon Steve, and it wouldn’t change what it is.

At this point, the most noteworthy thing about the split infinitive is that there are still some people who think there’s something wrong with it. The original objection was that it was wrong because uneducated people used it and good writers didn’t, but that hasn’t been true in decades. Most usage commentators have long since given up their objections to it, and some even point out that avoiding a split infinitive can cause awkwardness or even ambiguity. In his book The Sense of Style, Steven Pinker gives the example The board voted immediately to approve the casino. Which word does immediately modify—voted or approve?

But this hasn’t stopped The Economist from maintaining its opposition to split infinitives. Its style guide says, “Happy the man who has never been told that it is wrong to split an infinitive: the ban is pointless. Unfortunately, to see it broken is so annoying to so many people that you should observe it.”

I call BS on this. Most usage commentators have moved on, and I suspect that most laypeople either don’t know or don’t care what a split infinitive is. I don’t think I know a single copy editor who’s bothered by them. If you’ve been worrying about splitting infinitives since your high school English teacher beat the fear of them into you, it’s time to let it go. If they’re good enough for Star Trek, they’re good enough for you too.

But just for fun, let’s do a little poll:

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