These two principles do not belong, at least not yet, to the core propositions underlying the science of central banking not because their content is not important but for other reasons.
In the case of the policy rules, the simple reason is that they are not used – by most central banks – in the actual conduct of monetary policy, although they may be used for analytical purposes and as benchmarks for comparison of the policies implemented in practice. There are several reasons why such rules are not used in the practice of monetary policy.