CMOS has not, since the thirteenth edition (1983), frowned on the split infinitive. The sixteenth edition suggests, to take one example, allowing split infinitives when an intervening adverb is used for emphasis (see paragraphs 5.106 and 5.168). In this day and age, it seems, an injunction against splitting infinitives is one of those shibboleths whose only reason for survival is to give increased meaning to the lives of those who can both identify by name a discrete grammatical, syntactic, or orthographic entity and notice when that entity has been somehow besmirched. Many such shibboleths—the en dash, for example—are worthy of being held onto. But why tamper with such sentences as the following?Oxford more or less agrees, asserting as follows: "The ‘rule’ against splitting infinitives isn’t followed as strictly today as it used to be. Nevertheless, some people do object very strongly to them. As a result, it’s safest to avoid split infinitives in formal writing, unless the alternative wording seems very clumsy or would alter the meaning of your sentence," and The Guardian and Observer style guide notes:
Its five-year mission is to explore new worlds, seek out new life and new civilizations, to boldly go where no man has gone before.It seems to me that, at least given these two examples, euphony or emphasis or clarity or all three can be improved by splitting the infinitive in certain situations. It’s one of the advantages of a language with two-word infinitives. One might observe, for that matter, that English infinitives are always split—by a space.
His first thought, when something went wrong, was to immediately hit the escape key—even when he was nowhere near a computer.
Raymond Chandler wrote to his publisher: "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." And after an editor tinkered with his infinitives, George Bernard Shaw said: "I don't care if he is made to go quickly, or to quickly go – but go he must!"Wikipedia, of course, has much to say on the controversy, but is it one? I guess the question is this -- is this something about which you care at all, or are you going to willy-nilly split your infinitives when writing?
added: Poll results! Split infinitives -- "whenever you feel like it" (53%) wins over "sparingly" (40%) and "never" (5%).