This paper concerns a (prospective) goal directed proof procedure for the propositional fragment of the inconsistency-adaptive logic ACLuN1. At the propositional level, the procedure forms an algorithm for final derivability. If extended to the predicative level, it provides a criterion for final derivability. This is essential in view of the absence of a positive test. The procedure may be generalized to all flat adaptive logics.
The problemInference relations for which there is no positive test abound in both everyday and scientific reasoning processes. 1 Adaptive logics are a means for characterizing such inference relations. The characterization has a specific metalinguistic standard format. This format provides the logic with a semantics and with a proof theory, and warrants soundness, completeness, and a set of properties of the logic. 2 The first adaptive logics were inconsistency-adaptive. The articulation of other adaptive logics provided increasing in-E-mail address: Diderik.Batens@ugent.be (D. Batens). 1 A positive test is a systematic procedure that, for every set of premises Γ and for every conclusion A, leads after finitely many steps to a "yes" if A is a consequence of Γ . Remark that the consequence relation defined by classical logic is undecidable, but that there is a positive test for it-see [26] for such matters.2 Onlypart of these results are written up, viz. in [17].1570-8683/$ -see front matter