On degrees of truth, partial ignorance and contradiction

Didier Dubois

In many works dealing with knowledge representation, there is a temptation to extend the truth-set with values expressing ignorance and contradiction. This is the case with partial logic and Belnap bilattice logic. This is also true in interval-valued extensions of fuzzy sets. This paper shows that ignorance and contradiction cannot be viewed as additional truth-values nor processed in a truthfunctional manner.

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