Serious argumentation is not about opinions but about gaining orientation in new realms of reality. From a pragmatic point of view, orientation is the function of theory. In order to develop this view, the pragmatist and neopragmatist philosophy is critically examined. A concept of successful praxis is established as a basis of theoretical understanding. The growth of understanding is modeled as a differentiation of the theory concept into epistemic (old) and thetic (new) theory. Based on this, extensive conceptual clarifications of knowledge and truth are carried out with regard to the role of argument and via the critical examination of the respective work in analytical philosophy (e.g. the Gettier problem).