At central banks around the world, including the Bank of England, Sweden's Riksbank, Norway's Norges Bank, and the Reserve Bank of New Zealand, policy is conducted on the basis of "inflation-forecast targeting": the central bank constructs quantitative projections of the economy's expected future evolution based on the way in which it intends to control short-term interest rates, and public discussion of those projections plays a critical role in justifying the banks' conduct of monetary policy to the public. What accounts for the appeal of this approach? Should it be adopted more widely or more explicitly? I review the long-running debate between proponents of monetary rules and proponents of discretionary monetary policy and argue that in...