At Regensburg the Holy Father argued that faith and reason need each other as paths to truth. Benedict defended this as an essential part of Christian belief because the God who reveals Himself (faith) is also the author of the natural order and the human capacity to understand it (reason). The Pope highlighted that the prologue of John’s Gospel begins, “In the beginning was the word (logos),” and logos is the Greek word for reason. God is reasonable, and so to act contrary to reason is to act contrary to God.

Benedict asks if Islam conceives of God in the same way. Does Islam have an equivalent to the divine logos?  Benedict raised the question of whether the Islamic conception of God as utterly transcendent, beyond all human categories, means that God is beyond reason itself. The suggestion is not that Allah is crazy or insane, but rather that he is not bound by a reason accessible to human beings.

Faith without reason gives rise to fundamentalism. Reason without faith produces a secularism that cannot address the most fundamental human questions about origin, destiny and meaning. The bulk of Benedict’s address was directed against the latter phenomenon, criticizing a modern secularism that has nothing to say to people of faith and nothing to say about the foundations of human culture. In criticizing the neglect of reason in favour of faith alone, Benedict criticized a major figure in the history of Christian philosophy (Duns Scotus) who he considered to have made this mistake.

So why, if that was Benedict’s main point, get into Islam at all? Why the incendiary 14th-century quotation from Byzantine Emperor Manuel II Paleologus: “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.”

One of the potential consequences of a faith-only fundamentalism is violence. Violent force — which by its nature does not seek to persuade — can grow out of a zeal to convert without recourse to reason. It is simply a fact that Islamic violence is a pressing problem around the world. Muslims themselves are the first victims of it, but Christians in Islamic countries regularly face harassment and persecution. Benedict wants to clarify that the roots of this violence lie in a perversion of Islam, not its authentic theology. That’s a task only Muslims can accomplish, but the Pope has a pulpit sufficient to draw attention to the issue.

Benedict likely chose the dialogue between Manuel II and his Persian interlocutor because it deals directly with this question in a historically suggestive setting. Manuel II was one of the last Byzantine emperors; some 50 years after this dialogue Constantinople would fall to the Ottomans and the great Haggia Sophia church would become a mosque. Manuel II is an emperor under siege from Muslim armies — not only Muslim armies, as he was threatened at times by Christians too, but nevertheless with a concrete experience of the sword of Islam.

“The emperor goes on to explain in detail the reasons why spreading the faith through violence is something unreasonable,” said Benedict in the key passage that immediately followed the words that got all the attention.  “Violence is incompatible with the nature of God and the nature of the soul.”

He then quotes Manuel II on the key point: “God is not pleased by blood, and not acting reasonably 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...”

That is the point Benedict wants to raise in relation to Islam, because daily Christians are faced with the consequences of its opposite. Five years after Regensburg, with the Holy Father returning to Germany this week, that point is as urgent as ever.