In this study delusion is regarded from the aspect of a phenomenology of imagination. Delusion as an experience of fictitious actualities is interpreted as the attempt of a psychotic person, to find a sense of existence in view of the threat by mental illness. After explaining the philosophical fundamentals, imagination is considered to be the dynamic origin of delusion and hallucinations. The discussion of psychopathological and clinical problems is followed by a demonstration of further phenomenological and hermeneutic approaches.