In "The Cask of Amontillado" it is important that Fortunato should not be totally drunk when he goes to his death because if he is totally "out of it" the entire plan would be lost to him. Montresor is interested in revenge against Fortunato; in order for this to have the desired effect, Fortunato has to be aware of what is happening. Montresor wants him to feel the fear, the terror involved and to know that the reason for it is because of the wrongs he has done to him in the past. Hope this helps. Check out the link below for more information.