 In the Lorenzen and Lorenz tradition, dialogical logic uses concepts of both game and argumentation theory to provide a pragmatist approach to meaning and reasoning constituted during the interaction of two players arguing on a given thesis. The game rules allow these players to challenge the other’s statements or defend their own statements in such a way that one player wins and the other loses after a finite number of moves. The meaning of the logical constants is provided by a set of interaction rules (the local rules) and the dialogical equivalent of a demonstration is a construction of plays through which it is shown that one player may win whatever the other player’s moves may be (winning strategy). Thus, both the dialogical meaning of the logical constants and the dialogical conception of demonstration are constituted by interaction.