I was reminded of all this recently, when I read the edition by Professor Theodore Khoury (Münster) of part of the dialogue carried on - perhaps in 1391 in the winter barracks near Ankara - by the erudite Byzantine emperor Manuel II Paleologus and an educated Persian on the subject of Christianity and Islam, and the truth of both. It was presumably the emperor himself who set down this dialogue, during the siege of Constantinople between 1394 and 1402; and this would explain why his arguments are given in greater detail than those of his Persian interlocutor. The dialogue ranges widely over the structures of faith contained in the Bible and in the Qur'an, and deals especially with the image of God and of man, while necessarily returning repeatedly to the relationship between - as they were called - three "Laws" or "rules of life": the Old Testament, the New Testament and the Qur'an. It is not my intention to discuss this question in the present lecture; here I would like to discuss only one point - itself rather marginal to the dialogue as a whole - which, in the context of the issue of "faith and reason", I found interesting and which can serve as the starting-point for my reflections on this issue.
In the seventh conversation (διάλεξις - controversy) edited by Professor Khoury, the emperor touches on the theme of the holy war. The emperor must have known that surah 2, 256 reads: "There is no compulsion in religion". According to some of the experts, this is probably one of the suras of the early period, when Mohammed was still powerless and under threat. But naturally the emperor also knew the instructions, developed later and recorded in the Qur'an, concerning holy war. Without descending to details, such as the difference in treatment accorded to those who have the "Book" and the "infidels", he addresses his interlocutor with a startling brusqueness, a brusqueness that we find unacceptable, on the central question about the relationship between religion and violence in general, saying: "Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached.” The emperor, after having expressed himself so forcefully, goes on to explain in detail the reasons why spreading the faith through violence is something unreasonable. Violence is incompatible with the nature of God and the nature of the soul. "God", he says, "is not pleased by blood - and not acting reasonably (σὺν λόγω) is contrary to God's nature. Faith is born of the soul, not the body. Whoever would lead someone to faith needs the ability to speak well and to reason properly, without violence and threats... To convince a reasonable soul, one does not need a strong arm, or weapons of any kind, or any other means of threatening a person with death...".