The author distinguishes two concepts of practical reason: (a) practical reason as a source of practical principles, and (b) practical reason as the theory of thought operations connected with action. He proves that there is no practical recognition in the sense (a). We can deal with actions only on the basis of dichotomic semantics. Critical analyses of some theories of practical reason are presented (Kant, Lorenzen, Apel, Alexy). The critical part of the paper mainly concerns the discourse theory and its (...) implications for practical philosophy and jurisprudence. (shrink)