This paper scrutinizes some peculiarities of the culture of Internet argumentation: it is a qualitative pragma-dialectical study of different strategies arguers employ to question or attack argumentation of their opponents in online political discussion forums. The basic assumption of the paper is that this particular context of argumentation—or: argumentative activity type—creates special opportunities and constraints for critical reactions regarding propositional content and relevance of argumentation. These opportunities and constraints, it is argued, may lead online discussions to being endless, yet not (...) necessarily fruitless from an argumentative perspective. (shrink)