Atheists in the UK are banding together to finance an advertising campaign, in which the following will appear on the sides of buses: "There is probably no God. Now stop worrying and enjoy your life." - A letter in today's Guardian suggests that this "is a philosophy at the root of many of the ills of our society, including debt, addiction and environmental degradation." - Is God a killjoy? Is there any connection between non-belief in God and irresponsibility?