I don't remember much of Michael Nazir-Ali's Laing Lecture in 2009. But in staff prayers this morning, I was reminded of what he said about salt and light. Here is my paraphrase:
Light is all pervading. Where there is light, there can be no darkness. When Jesus talks about people being light, he is talking of light removing the darkness. However, much more effective in our culture is to be salt. Salt mixes in with food and flavours it. It doesn't get rid of the food, but changes the flavour of the meal.Let's be salt.