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Abstract. We consider a reinterpretation of the rules of default logic. We make Reiter’s default rules into a constructive method of building models, not theories. To allow reasoning in first order systems, we equip standard first-order logic with a (new) Kleene 3-valued partial model semantics. Then, using our methodology, we add defaults to this semantic system. The result is that our logic is an ordinary monotonic one, but its semantics is now nonmonotonic. Reiter’s extensions now appear in the semantics, not in the syntax. As an application, we show that this semantics gives a partial solution to the conceptual problems with open defaults pointed out by Lifschitz [16], and Baader and Hollunder [2]. The solution is not complete, chiefly because in making the defaults model-theoretic, we can only add conjunctive information to our models. This is in contrast to default theories, where extensions can contain disjunctive formulas, and therefore disjunctive information. Our proposal to treat the problem of open defaults uses a semantic notion of nonmono-tonic entailment for our logic, deriving from the idea of “only knowing”. Our notion is “only having information ” given by a formula. We discuss the differences between this and “minimal-knowledge ” ideas