  Suppose that we start with a domain of discourse, D, and an interpretation of the predicate F and the relation symbol R. Gupta and Belnap's revision-theoretic treatment of concepts thus circularly introduced allows one to give categorical verdicts, for certain d ∈ D about whether or not d satisfies G. Other objects will be unstable relative to G: we will be able categorically to assert neither that d satisfies G nor that d does not satisfy G. In the case of truth, Gupta and Belnap take the set of T-biconditionals of the form