Are Islamist suicide bombers motivated by obedience to the God of the Qu'ran, or simply violent people using Islam as a cover story? Most sensible people want God to be at least moderately likeable, but what about a God who is apparently a militant, avenging purist? Is begs the question, what is God really like, and whose God is the real God?
The Religions of the Book (Judaism, Christianity, Islam) find their ideas about God from the written word. For followers of these three monotheistic religions, the concept of revelation is key. God takes the initiative and reveals something of him*self, through dreams, visions, voices, supernatural events, people. So we don't invent our religion (adopting a kind of do-it-yourself spiritual toolbox) we receive God's own revelation of himself through the scriptures, which we are enjoined upon to read.
The philosophical idea behind the concept of a Holy Book is that if God exists, and is at all knowable to humans, he must be like something we can understand. So people who claim to know God, say he is characterised by love, or mercy, or peace, or purity, or ...fill in the blanks. How do we know? We know because he 'contacted' us before we contacted him. In the case of Christianity, we go one step further and say that he became one of us to make it as clear as possible. To the question, What is God like? the Christian answers, look at Jesus.
Practically, it matters what God is like because followers of a religion are bound to become like the God they worship. So sacred writings are important. The book moulds the person, so to speak. It is a misunderstanding to assume that only religious people are moulded, while everyone else is 'neutral' and cooly choosing their own identity in some philosophical vacuum. In point of fact, we're all being moulded by something or somebody; it's just that some of us are more aware of it than others.
People of the Book do have issues with their books though. It's not as straightforward as reading your Book and then knowing what to do, how to be, in every situation. So the problematic terrain around militant Islamist motivation can be boiled down to one question: how do religions interpret their texts?
It would appear that the Qu'ran contains so-called 'sword verses' alongside 'peace verses'. Clearly if you read a 'sword verse', like 'and slay them wherever you find them and drive them out of the places whence they drove you out' (Qu'ran 2:191) it's going to look like Islam is promoting violence. But then you might also read 'fight in the cause of Allah those who fight you but do not transgress the limits, for Allah loveth not transgressors', which you could read as sanctioning self defence, but no more (Qu'ran 2:190).
The Bible is also a mixture of texts which may be taken different ways, according to their interpretation. This was the whole issue around whether women could minister equally in the Church of England. Some texts of St Paul do illustrate restrictions on women's roles, as they were being worked out then, while others suggest that equality in the early Christian communities began to develop very fast. The arguments about whether gay unions may be sanctioned by the Church are another example of different readings of texts, with new readings challenging traditional readings, and each group claiming to know what God says on the subject.
When Christians have disagreed about the interpretation of their texts, depending on the century they were in they have either burned each other at the stake (16th century, regrettable) or argued endlessly on Twitter about it (21st Century, preferable). Sitting down and talking about disagreements is now thought of as a mark of a civilised society, and rightly. It brings to mind a lovely invitation in the Old Testament where God says, 'come now let us reason together' (Isaiah 1:18, KJV). It seems that God is at least as interested in how we argue, as in what we're arguing about (and perhaps more so).
So what to make of IS? Whether we think of this frightening phenomenon as in any way connected to Islam is important, because it feeds into how we view Islam in general and the Muslims we live amongst in particular.
It may be we don't need to look further than Jesus' injunction, 'by their fruits shall you know them' (Matthew 7:20). For the People of the Book, it can never be just about a blind 'which words shall we follow today?' but a living out of faith in the spirit of humility, goodness, love and all the other 'fruits' that the average person will tell you are the pre-requisites of being a decent human being, let alone a religious one. By that simple test, IS does not qualify.
*the impossible pronoun question means God has to be referred to as either he or she or both. For ease and simplicity, I'm still in the habit of referring to God as 'he', whilst realising the limitation of the English Language and the implied theology of using 'he'.