A correspondent writes to ask about split infinitives. He has read The Fight for English, where I say that the construction has been in the language for centuries, but I don't give any examples. He is suspicious. Are there really any before the 19th century, he asks?
Oh, yes, plenty. They've been traced back to the 13th century, at first usually with a single negative word or pronoun as the splitting element, but then with adverbs. The early 15th-century cleric Reginald Pecock frequently used them. Here is an example from his The Repressor of Overmuch Blaming of the Clergy (chapter 5):
Goddis forbode y schulde be so lewde for to so seie
[God forbid I should be so foolish as to say so]
There are examples in Wyclife, Tyndale, More, Donne, Goldsmith, Burns... From Thomas More (1557) we find 'and then to not byleve them'; from Thomas Stapleton (1565), 'to flatly gainsaye'.
The practice became less common in the Early Modern English period - I don't know why. I can't recall any instances in Shakespeare, for instance. It builds up again in the 18th and 19th century - which is presumably why late 19th-century prescriptive grammarians started to condemn it - notwithstanding instances such as 'in order to fully appreciate' from Lord Macaulay (in 1843), among others.