The recent terrorist attack in Barcelona is not the first to have involved a vehicle driving onto a pavement and ploughing through a crowd of people.
This terrifyingly simple tactic works because we depend on drivers keeping their vehicles off the pavements so that we can walk safely.
Our lives are full of dependency, and this was brought home to me very strongly some years ago, while I was working for a few days at a private university in Cairo.
The students came from wealthy families, and the catering outlets on the campus were major international brands- reliable, you’d think.
One morning I noticed a queue of students outside one of the outlets getting a bit restive: there was no food!
It turned out that this was nothing to do with the retailer, but the food delivery company, although it had the usual supply of burgers and buns, was unable to reach the campus because the motorway was blocked by trucks that had run out of diesel.
They had run out of diesel because there had been no delivery to some of the filling stations.
My local colleagues explained that there had been glitches in the administration associated with the export of Egypt’s crude oil, and less money had come into the country, so that it could not pay for all the fuel it needed to import.
Complicated, isn’t it?
It also turned out that this had caused food prices to double in some areas in a matter of weeks, and was responsible for the fact that the electricity and the water supplies were being turned off for several hours each day, because the utility companies were working at reduced capacity.
We don’t usually see this type of dependency in Britain, because our systems are relatively mature and change slowly; in developing regions, things change much more quickly, so they go wrong more often and show how much a failure impacts on all of us.
But the dependency is there, just the same, in our families, our communities, our nation and our international relationships.
We tend to view independence as virtuous, and feel something is lacking in people who are dependent.
But God made us to be dependent on him and on each other, and virtue lies in valuing those we depend on and those who depend on us.