A pretty good explanation of the subject.
A Dictionary of Modern English Usage by H. W. Fowler
I found this @ http://catholicinsight.com/a-diction...-english-usage
and wanted to share it with my fellow writers.
Oxford at the Clarendon Press, London, 1926
Split Infinitives. The English-speaking world may be divided into (1) those who neither know nor care what a split infinitive is; (2) those who do not know, but care very much; (3) those who know and condemn; (4) those who know and approve; and (5) those who know and distinguish.
Those who neither know nor care are the vast majority, and are a happy folk, to be envied by most of the minority classes; “to really understand” comes readier to their lips and pens than “really to understand,” they see no reason why they should not say it (small blame to them, seeing that reasons are not their critics’ strong point) and they do say it, to the discomfort of some among us, but not to their own.
Read the full piece at the link.