Based on a phenomenological analysis of psychotic interpretation of the world concretism is supposed to represent an important mechanism of schizophrenic thinking: Schizophrenic concretism is the result of an ontological regression of cognitive functioning onto the archaic level of actional representation. Following Jean Piaget's theories about the children's constructions of reality a hypothesis about the structure of psychotic interpretations of the world is being proposed: In psychotic thinking the knowledge about the world is structured in an adualistic way which is characterized by an alloy of significance and notion, inner and outer world, physis and psyche. The structural similarity of psychotic thinking and thinking in early developmental stages is illustrated concretely on the basis of examples. Fundamental differences between childish and schizophrenic ways of interpreting the world will be presented, showing the specificity of cognitive representation in schizophrenic thinking.