David Lewis et la rationalité des conventions

Lewis sets out to give meaning to the notion of language convention based on the coordination of rational agents.To do so, he makes use of coordination games which require concepts such as the common knowledge of rationality that turn out to be disputable. Consequently, the link he proposes between convention and rationality appears to be at the same time too strong and too weak. On the one hand, it is hard to demonstrate that conformity to a convention as defined by Lewis may arise from a purely rational behaviour.On the second hand, the concept of convention he uses rules out coordination games in which individual rationality leads to suboptimal choice.