To-infinitives such as to go, to catch, to see, etc. are the ‘infinitives’ that people mean when they talk of split infinitives. Split infinitives are usually frowned upon by those who mention them. A sentence like He wants to actually see them leave is said to contain a split infinitive because the word to is separated from the word see. The descriptive linguist is concerned with what splittings of infinitives actually occur in the usage of English speakers. The usage is systematic and, as such, can be studied and described. For instance, only certain constructions are observed to occur. Nobody attests the occurrence of an expression like *He expects to the train meet, instead of He expects to meet the train. But expressions like He expects to suddenly see them do occur; that is, there is a certain predictability about them. Upon reflection, of course, we realize that if this kind of expression did not have a systematic existence in the English language, there could not be any tradition about split infinitives being a ‘bad thing’. If they occurred only randomly, as a result of ‘crossed wiring’ in the execution of speakers’ plans—like
spoonerisms—nobody would have anything to that they were accidental. In the study of the sociology of language, however, it is interesting that the ‘anti-split-infinitive’ tradition exists; it is part of the social distribution of beliefs about
the language.