Sex. We all talk about it, read about it, write about it, watch a film. Think about it, dream about it, long for it, thirst it, quench it, love it, hate it; do it, don't do it. We do it with lovers, strangers, husbands, wives, one night stands. It can make relationships, break relationships. Priests do it, teachers do it, parents do it, children do it. For right or wrong, every now and then, we all need a bit of filth.