To explain wish-fulfilment in dreams and neuroses real memories are needed in addition to the wish. Reassurances cannot be created but must be constructed from actual past experiences, and any distortion of reality by dreams or symptoms in failure of reassurances will be followed by a compensatory tendency to correct such distortions. The fundamental differences that distinguish rational waking behaviour from neuroses and dreams are based upon the quantitative relationship between the ego's capacity for synthesis and the intensity of conflict. Neuroses and dreams deal with conflict in a fragmentary way, repeating, because of the ego's inadequate synthetic power, previous reactions to the traumata. Rational behaviour requires an ego span sufficient to view the total situation and also to pay attention to differential criteria so as to be able to learn from past mistakes instead of repeating them.