Dreams

"My life, as it passed thus, was indeed hateful to me, and it was during sleep alone that I could taste joy.  O blessed sleep!  often, when most miserable I sank to repose, and my dreams lulled me even to rapture."  (Frankenstein p. 151)

In the novel, sleep is an important symbol.  Whenever Victor is feeling most miserable, he sleeps to escape reality.  On p. 135, Victor even mentions developing an addiction to sleeping pills.  When Victor is most troubled, he has nightmares about the creature.  I believe these nightmares represent the guilt Victor feels for creating this monster.  Later in the novel, Victor enjoys his dreams because they allow him to escape from his hellish-nightmare of a life.  After all, his mother, father, sister/wife, friend, and brother are dead.  Since Victor's dreams consist of the images of his loved ones, he begins to cherish the times he is asleep over the times he is awake. 

Images of sleeping contribute to the theme of solitude in the novel.  Victor seeks this solitude to escape from his own reality of life.  Early in the novel, solitude in nature causes Victor to heal his scarred mind, but later, he can only reach a sense of peace through drugs and sleeping.  I think this kind of solitude in sleep relates to death.  Since he has lost everything good in his life, he welcomes death with open arms.  Sleep is just a way to feel that high of death without actually dying.