Reasoning About Permission and Obligation

Abstract

How is deontic logic possible on a positivistic philosophy of norms? D. Makinson (1999) considered this question the ‘fundamental problem of deontic logic’, and called to reconstruct deontic logic as a logic of reasoning about norms. A solution is to use a semantics which defines the truth of monadic and dyadic deontic sentences with respect to an explicitly modelled set of norms. Here, I explore how such a norm-based semantics can be adapted to include not just mandatory but also permissive norms that possibly conflict with the first, and describe how this may affect the validity of well-known theorems. All studied proposals are based on a definition of consistency from the later theory of G. H. von Wright. The approach may shed new light on the problem of ‘free choice permission,’ while D. Lewis’s ‘problem of permission’ persists. Finally, I question a persistent belief about permissions: that unlike obligations they must be considered one by one, and not collectively.