If whoever bombed the Madrid trains aimed to make those living in crowded European cities feel more vulnerable, they’ve probably succeeded, if only because it’s hard to ignore the films and pictures of the aftermath. Without paying a penny, euro or dollar, modern terrorists gain maximum coverage from the modern media, encouraging a siege mentality. The trouble is, the more frightened people are, the less clearly they think about the threat, and how to deal with it.

In countries like Columbia or Northern Ireland, ordinary people have been living with terrorism for years. Across Africa and Eastern Europe, random acts of violence are commonplace. That’s terrorism too – it just doesn’t make the news so often. Killing people in ones and twos doesn’t attract the same sort of publicity or sense of outrage as the destruction of the Twin Towers or the Bali bombing.

Terrorism may be motivated by nationalism, religious fundamentalism or just sheer nastiness – people with warped minds carrying out despicable acts. What terrorists have in common is that they take a ‘them and us’ mentality to extremes. They regard anyone who isn’t one of them as less than human and totally expendable.

Whatever else we do about terrorism, such as increasing our vigilance and internal security, we must be very, very careful that we don’t fall into the trap of regarding anyone who’s different from us as a potential threat. For example: a lot of what’s been written on the asylum and immigration issues in the tabloid press over the last couple of years has been thinly disguised xenophobia, expressing a fear or hatred of strangers. Hatred prevents us from seeing other people as human beings, and that’s how terrorists think.