People are motivated by all sorts of things: money, fame even notoriety although I guess few of us have been motivated by a crocodile. But this was precisely the technique that one Australian swimming teacher wanted to adopt a few years ago. Mark Biggles, who taught swimming in Darwin, reckoned that "a croc", drugged and with its jaws wired shut, was just what his young protégées needed. Not surprisingly the City Council disagreed and refused to allow his idiosyncratic experiment.

I was reminded of Mark Biggles when reflecting on the brutal murder of drummer Lee Rigby. Like everyone else I was both horrified and amazed to see an articulate young man waving a machete in his bloodied hand and supposedly claiming that he had the right to behead those who insulted his faith, and it left me struggling for an explanation.

The commentators have not been slow in offering their suggestions of course, and Dominic Lawson's article in the Sunday Times was particularly insightful. According to Lawson we need to come to terms with what 'toxic maleness'. The male brain, he says, works in such a way that men tend to treat human beings as cogs in a machine in contrast to women who display far more empathy (to the point where they can even treat objects as if they have feelings!).

I am not qualified to comment on that assertion but Lawson was surely right to suggest that many modern terrorists have allowed their personal sense of injustice to be subsumed into a wider cause. And in arguing this Lawson pointed to a key factor in all such atrocities.

We dare not ignore the role of "ideas" (the "controlling narrative") for what we believe determines what we do. I have witnessed this on many occasions, not least when visiting the Balkans in the early 1990s. I can still recall a well-known surgeon telling me for example, that much of the appalling cruelty we were witnessing could be explained by what had happened, or what people thought had happened, more than half a century before.

Solomon hit the nail on the head when he suggested that a man is what he thinks. But it's just as true of women too as we can see from the incredible behaviour of Ingrid Loyau-Kennett. Loyau-Kennett gained worldwide fame after she was filmed talking to one of the alleged Woolwich terrorists. She will live long in the memory because she had the courage to look him in the eye and say "You are going to lose".

And she has told us why she did it. She got off her bus, she says, because her Christian faith kicked in when she thought someone had been injured in a car accident. "I live my life as a Christian," she told a reporter later. "I believe in thinking about others and loving thy neighbour. We all have a duty to look after each other". And in another telling comment she added "A whole group of people walking towards those guys would have found it easy to take those weapons out of their hands. But me on my own I couldn't."

It made me wonder how I would have reacted if I had been in Loyau-Kennett's place. Being a Good Samaritan can be a risky business.