Eugene Bleuler was one of the first to emphasize the importance of affect and its pro‐ nounced impact upon the course and outcome of psychosis. The famous “Krapelian dichtoco‐ my” which supported the clear distinction between mood and psychotic illnesses on the basis of etiological origins, symptomatology, course and outcome was first challenged by Bleuler. Bleuler recognized the disorders of affect as one of the four primary symptoms (blunted 'Affect', loosening of 'Associations', 'Ambivalence', and 'Autism') of schizophrenia, as opposed to delusions and hallucinations which were perceived as secondary. Bleuler further postulated the incongruity between emotions and thought content in people with schizo‐ phrenia as well as their diminished or complete lack of emotional responsiveness. Bleuler’s recognition of the importance of affective disturbances in schizophrenia has influenced cur‐ rent diagnostic definitions and criteria of schizophrenia.