Over the course of the twentieth century, economic policy increasingly took on the obligation of maximising household welfare subject to available resources in the presence of markets that need regulation, information, co-ordination and the ready supply of public goods. Within that large set of policies – ranging from education to defence – which manage a complex economy that sits itself within a world of exchange and trade, what do central bankers seek to do? The imperative to stabilise is clear. This is not so much a problem about exploration, experimentation and innovation but about creating conditions under which plans can be formulated and exercised with some degree of certainty that monetary and financial exchange will be safeguarded.