Abstract: The standard logical approaches to model argumentation forms that involve defeasibility stress either the point on the non monotonic property of the turn-style or introduce a specific conditional (or a combination of the two). In a game-theoretic approach this means that either it is a property of winning strategies or it is about the rules that define a new logical constant (particle rules). In the present paper we will make use of an alternative to the approaches mentioned about available to the dialogical approach. The dialogical approach, as developed in the appendix, distinguishes between · the rules defining the constants (local meaning), · the rules that determine how to play (global meaning) and · the rules that delineate the ways to win (strategic level) if winning is possible · the notion of winning at play level from winning at the strategic level In this context, defeasible reasoning is about introducing some restrictions on the rules on how to play (global meaning), it consists neither in introducing a new conditional (at the local level) nor in changing the winningstrategies. According to our view, defeasibility principle involves semantic features at the global level. More precisely, according to the dialogical approach, defeasibility amounts to the task of verifying that the proponent’s thesis is compatible with the last concession(s) introduced in the play. Notice that the theory of meaning underlying dialogical logic provides a uniform semantics that though it is neither model-theoretic non-prooftheoretic can capture the features of both of those approaches within one frame. Moreover, this approach allows to distinguish John Pollock’s justification of a belief relative to the actual defeasible reasoning at a given stage from warrant which assumes the set of all possible inferences that can be drawn by an idealized player at a given stage. In the dialogical framework, while warrant corresponds to the strategic level (triggered by the extensive form of the play at a given stage) justification corresponds to the play level. Precisely the dialogical level where the semantics is generated and where Pollock’s notion of multiple assignments find its natural place. It should be also pointed out that the dialogical framework provides to the development defeasible reasoning a level beyond the one of play and strategy: the level of cycles linked to the notion of dialogue-defineteness Dialogical defineteness is the dialogical way to deal with Church’s theorem on the non-decidability of first-order logic. The analysis of defeasible reasoning within the dialogical framework should help to build a link between the approaches of default-logic and the argument-based approach initiated by John Pollock [1987], which defines notions like argument, counterargument, attack and defeat, and defines consequence notions in terms of the interaction of arguments for and against certain conclusions.