This combination can only be squared if they have a clearly defined mandate for which they are held accountable by the public. It is legislators that define the mandate that establishes the goals of monetary policymaking. And it is legislators that are responsible for holding central banks accountable for the effectiveness of their monetary policy.
But for effectiveness, credibility is essential, and therefore legislators must want a credible central bank. Credibility hinges on independence: the central bank should not be subject to fiscal or political dominance and should be free to choose the instruments that are most appropriate to deliver its mandate.