A 1996 Debate with Nuel Belnap on the Thin Red Line

Abstract This paper examines a 1996 debate with Nuel Belnap on the thin red line (TRL) in branching-time semantics. While A.N. Prior’s tense-logic did not incorporate a privileged future, he discussed the idea as a possible interpretation of Ockham’s logic. The TRL asserts that one future among many is “true”, preserving bivalence, but Belnap and Green (Philos Perspect 8:365–388, 1994) argued that this contradicts indeterminism. The paper explores the origins of the term “thin red line”, Belnap and Green’s objections, and refinements to the TRL, conceived as a dynamic function for selecting a privileged chronicle at each moment in a branching time model. It also examines Belnap’s response to these refinements and situates the debate within broader discussions on Ockhamism and Molinism.