Very Misc. On 'they' (but not They) ...From an American Scholar article

[Mark Kohut]

According to modern-day grammar books, “they” as a singular, gender-neutral pronoun (e.g., I saw someone, but I don’t think they saw me) is incorrect, since a plural pronoun cannot describe a singular referent. And so we have settled on the generic “he.” This is, we are told, the way things have always been—good enough for Jonathan Swift or Jane Austen.Except that what was in fact good enough for Swift and Austen was “they.” As Ann Bodine argues in her 1975 article “Androcentrism in Prescriptive Grammar,” prior to the 19th century, “they” was commonly—and uncontroversially—used as a generic singular pronoun. Grammarians were the ones who inserted the generic “he” into English about 200 years ago in an effort to improve the language.