Not that most of us care. If asked what's wrong with Star Trek's aim, "to boldly go where no man has gone before," we're likely to point out its sexism, not its placement of the word "boldly." But if you harbor any residual guilt about split infinitives from long-ago English classes or from several decades of of copyediting, here's good news.
Structurally speaking, it makes no sense to say that the infinitive in Star Trek's mission statement is "to go." Nope. The infinitive is "go." Just plain "go."
In other European languages, the infinitive is one word, not two. "Go," for example, is aller in French. "To go to France" is aller en France. But the French, like the English, often use little words like the English "to" when a sentence has two verbs. "He begins to read" is il commence à lire, and "she decides to leave" is elle décide de partir.
Why then do English speakers say that the infinitive is "to read" and "to leave," while French speakers do not say it is à lire and de partir?
Well, one explanation is that in French, depending on the sentence, the same infinitive may require "à" or "de" or no preposition at all. In English, by contrast, the "to" is always required ... except that it isn't.
Yes, we always say "I want to go," never "I want go," and even though le prince du Danemark said "être ou ne pas être," the original Hamlet said "to be or not to be."
But we never say "I must to go" or "I can to go" or "I may to go" or "I had better to go" or "I should to go." And in all of these sentences, the second verb is most definitely an infinitive.
So why should even the most rigorous grammarian have "to go boldly" when he or she "can boldly go"? No reason at all : the infinitive, even though often coupled with "to," is simply "go." You can split it from its preposition, but you can't split the infinitive itself.
Blair Shewchuk, CBC News Canada's Senior Editor of Journalistic Standards, would probably disagree with my analysis (everyone does). He quite cheerfully approves separating the "to" from the verb, however, and that's what counts. In "To Boldly Split Infinitives," a delightful summary of the debate, he tells of one author with the right spirit:
In a letter written in 1947, U.S. author Raymond Chandler put it this way: "Would you convey my compliments to the purist who reads your proofs and tell him or her that I write in a sort of broken-down patois which is something like the way a Swiss waiter talks, and that when I split an infinitive, God damn it, I split it so it will stay split."I like that. It's bold.