Just shooting from the hip ... I can't think of a single person from the 17th or 18th century in my families, who has a confirmed middle name. I can't even think of anyone with a hidden middle name eg William P Lastname: no use of initials. For example, in the Helm family espec. in Frederick Co, where there numerous Williams, Thomases, Merediths &c it's very difficult to separate them in the legal system and land records. You'd think that if they had middle names or initials, they would have used them, or the courts would have required it of them. Instead they struggle with Jnr and Snr (whose senior to whom? How many diff't Jnrs can there be &c). In the 19th century middle names are everywhere and we often see people using a middle name, switching the order, or switching back and forth!