This can be regarded as a more general approach to representing uncertainty than the Bayesian approach.

Bayesian methods are sometimes inappropriate:

Let A represent the proposition *Demi Moore is attractive*.

Then the axioms of probability insist that

Now suppose that Andrew does not even know who Demi Moore is.

Then

- We cannot say that Andrew believes the proposition if he has no idea what it means.
- Also, It is not fair to say that he disbelieves the proposition.
- It would therefore be meaningful to denote Andrew's belief of
*B*(*A*) and as both being 0. - Certainty factors do not allow this.

dave@cs.cf.ac.uk