One limitation of a psychodynamic appraoch include untestable concepts. Popper argued that they psychodynamic approach does not meet the scientific criterion of falsification, in the sense that it cannot be disproved. Many of Freud's concepts, such as the Id or the Oedipus complex, occur at an unconscious level making them difficult, if not impossible to test. This means that Freud's ideas lack scientific rigour, the theory is pseudoscience rather than real science