The operative approach in the theory of truth in Kamlah’s and Lorenzen’s Logische Propädeutik was an attempt to create a scientific language by means of critical reconstruction of ordinary language. In Kamlah’s and Lorenzen’s opinion, the proposition is true only when it is interpersonally verified: the predicator „true“ helps to introduce the predicator „real“. The criterion of truth based on interpersonal verification seems to be insufficient compared with 0. Muck’s operative criterion of assertability. Kamlah’s and Lorenzen’s conception of the ontic comprehension offers no sufficient basis for their criticism of ontology.