Calibration and the Expert Problem

A decision maker needs to give his subjective probability for a single event of interest, A. Being aware that he has little substantive knowledge of the factors affecting A, the decision maker asks an expert for advice. The expert gives his subjective probability for A. In the light of this information, how should the decision maker form his subjective probability? In particular, does it matter to the decision maker whether the expert is a well-calibrated probability assessor? In this paper these questions are explored and it is suggested that concepts such as calibration and refinement cannot usefully be defined independently of the decision maker.