It uses idiographic methods but applies them nomothetically to large populations. freud developed an idea of the oedipus complex from a case study of a boy known as Little Hans who had a fear of horses. this is a problem as freud assumes all children will go through this complex, despite only having studied one individual ,whose experiences cannot be generalised to the whole population. So it is limited as we don't know if the theory is accurate for all individuals or only applies to little hans