``Put bluntly: data cannot ever speak entirely for themselves: every prior specification hassomeinformative posterior or predictive implications; and `vague' is itself much too vague an idea to be useful. There is no `objective' prior that represents ignorance.

On the other hand, we recognize that thereisoften a pragmatically important need for a form of prior to posterior analysis capturing,in some well-defined sense, the notion of the prior having a minimal effect, relative to the data, on the final inference. Such areference analysismight be required as an approximation to actual beliefs; more typically, it might be required as a limiting `what if?' baseline in considering a range of prior to posterior analyses, or as adefaultoption when there are insufficient resources for detailed elicitation of actual prior knowledge.

The curious reader may take a look at the (Bernardo and Smith 1994) and references cited therein, as well as at Bernardo (1997)....From the approach we adopt, it will be clear that thereference priorcomponent of the analysis is simply a mathematical tool. It has considerable pragmatic importance in implementing areference analysis, whose role and character will be precisely defined, but it is not a privileged, `unique non-informative' or `objective' prior."