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Afraid of `prejudices'? Inevitability of principle and frequent practical irrelevance of the priors

Doubtless, many readers could be at a loss at having to accept that scientific conclusions may depend on prejudices about the value of a physical quantity (`prejudice' currently has a negative meaning, but in reality it simply means `scientific judgement based on previous experience'). We shall have many opportunities to enter again into discussion about this problem, but it is important to give a general overview now and to make some firm statements on the role of priors.

In conclusion, contrary to those who try to find objective priors which would give the Bayesian theory a nobler status of objectivity, I prefer to state explicitly the naturalness and necessity of subjective priors[22]. If rational people (e.g. physicists), under the guidance of coherency (i.e. they are honest), but each with unavoidable personal experience, have priors which are so different that they reach divergent conclusions, it just means that the data are still not sufficiently solid to allow a high degree of intersubjectivity (i.e. the subject is still in the area of active research rather than in that of consolidated scientific culture). On the other hand, the step from abstract objective rules to dogmatism is very short[22].

Turning now to the more practical aspect of presenting a result, I will give some recommendations about unbiased ways of doing this, in cases when priors are really critical (Section [*]). Nevertheless, it should be clear that:


next up previous contents
Next: Recovering standard methods and Up: A probabilistic theory of Previous: Bayes' theorem for uncertain   Contents
Giulio D'Agostini 2003-05-15