(b) No, that's incorrect. Although it is important that judges do not exceed their powers, this is not the reason for the policy of requiring courts to follow earlier decisions.

The policy is expressed in the Latin phrase 'stare decisis', meaning 'let the decision stand'. This policy is the foundation of the doctrine of precedent and the basis on which previous decisions of the courts become a source of law.

The doctrine of precedent generally ensures that rules of law remain consistent, certain and predictable.