This paper is dedicated to the study on the Freud's psychoanalysis and Lacan's clinical theory in order to clarify the basic meaning of the structure, symptom, diagnosis and case study. There is no clear-cut demarcation between normality and pathology. There is a considerable overlap between the different categories. The psychoanalysis elaborates logically psychological birth of the human being as a subject. Especially it shows the depth exploration and intervention to the symptom and pathology, with pulling down the boundary between normality and abnormality. Freud finds out the means of diagnosis by structure not by phenomenal symptoms, and availability of diagnosis, ferreting out the pathogenesis of hysteria and neurosis. He pays special attention to a forced and arbitrary interpretation. He contends that interpretation is carried out only after a full analysis and conviction. We can devise more appropriate and effective treatments due to a psychic structure and schema. The mirror in which the baby can see its own reflection determines an overturning of the baby's perception of the world. According to Lacan this event takes place around the sixth month of life. Lacan's mirror stage is the first key to the symbolic and triad. Its a successive passage initiates neurosis and normal category in human development. Lacan reintroduce the father and the importance of the Oedipus complex as the founding moments of the introduction of the child to the other, which is outside the mother-child enclosure. The father functions as a symbol, the symbol of the limit to one-to-one relation. The vignette in this paper shows the clinical application of a mirror stage. The boy in this case accepted the father's name and symbolic other, went into the Oedipal triad, and achieved the position of subject by a analysis. Thus, his maladaptive problems diminished.