A main theme that is portrayed in this book is the topic of doubt. Nobody really knows anything and the only way you can prove if something is happening is through the Voigt Kampff test. Rick Deckard begins to wonder if he has feelings of empathy for androids. He ends up making love to Rachael Rosen and he realizes that he does have feelings for this particular android. His job he felt was always wrong since he killed people that were just like him. All of these thoughts brought him sadness and gave him a "mental breakdown." After was done killing the remaining androids he tried to look for reassurance on what he had done. He didn't know if he was right in doing what he did or if he was wrong.

This theme is a strong one since Mercerism is doubted and after being researched is proven to be false. The world that the people of Earth had always lived in was false as well. The sky was painted and Mercer wasn't even real or human. The whole scene of the "revelation" was just a couple of prerecorded videos of an old movie that happened long ago. Buster Friendly was able to report these breaking news to everyone who was listening. This gave a doubt to everyone who was listening. It was entertainment vs. religion and entertainment had won. Even so later on Rick Deckard comes across an old man who claims to be Mercer and ends up helping him as "god" usually does. We really don't know what is going on and it leaves a considerable amount of doubt that isn't answered.

In this quote we see that Buster Friendly is talking about how Mercerism never existed and that whatever people were believing was fake :

"Al Jarry made a repitious and dull film, a series of them in fact, for whom he knew not-and does not to this day. It has often been said by adherents of the experience of Mercerism that Wilbur Mercer is not a human being, that he is in fact an archetypal superior entity pergaps from another star....Wilbur Mercer is not human, does not in fact exist. The world in which he climbs is a cheap, hollywood, commonplace sound stage which vanished into kipple years ago." (209)

In this book there are many instances where the main characters begin to feel doubt for a decision they make or a decision they are about to make. One example of doubt was when Rick was in his house and began to feel empathy for the Androids. After he had killed three he didnt want to kill them anymore. Once he got to the apartment to anialate the remaining three, he began to have doubt if what he was doing should be done. Doubt is the feeling someone get or has when they begin to think twice of something there doing or going to do.