Performative contradiction are performative contradictions in this context. Habermas claims that post-modernism's epistemological relativism suffers from a performative contradiction. Hans-Hermann Hoppe claims in his theory of argumentation ethics that arguing for any political position other than free-market anarchism results in a performative contradiction. Jaakko Hintikka more rigorously fleshed out the notion of performative contradiction in analyzing Descartes' famous "cogito ergo sum" argument, concluding that "cogito ergo sum" relies on performance rather than logical inference. Performative contradiction A performative contradiction () arises when the propositional content of a statement contradicts the presuppositions of asserting it. An example of a performative contradiction is the
Cogito, ergo sum and that "I" know what "thinking" is. He suggested a more appropriate phrase would be "it thinks" wherein the "it" could be an impersonal subject as in the sentence "It is raining." The Danish philosopher Søren Kierkegaard calls the phrase a tautology in his "Concluding Unscientific Postscript". He argues that the "cogito" already presupposes the existence of "I", and therefore concluding with existence is logically trivial. Kierkegaard's argument can be made clearer if one extracts the premise "I think" into the premises "'x' thinks" and "I am that 'x'", where "x" is used as a placeholder in order to disambiguate