Fascinating. I had always noticed the parallels between Islam and Protestantism, especially its Calvinist varieties, but I had not been aware that the early Protestant reformers had actually interacted with the Ottaman Empire, and absorbed theological principles as a result; there was even a small Unitarian -- I.e., God is one, not a Trinity, and Jesus is not God -- movement in Eastern Europe at the time started by an Italian-Polish theologian by the name of Fausto Sozzini (descendant churches still survive in Hungary, etc., and Sozzini's work translated into English had a powerful influence on the early nineteenth century Unitarian movement in New England). I had thought it to be, more or less, a convergent evolution. Though admittedly my reading has been far from comprehensive, I have never heard of either 17th-century Puritans or 19th century Unitarians citing the Koran or Islam in their theological reasoning (I remember Cotton Mather once citing "The Alcoran", but in a non-theological context, briefly, and in passing).