Fear of Communism
Although this is a science fiction novel, the main theme within it is McCarthyism and the effect that it had on seemingly random law-abiding citizens. It also demonstrates that weeding out the left leaning had knock-on effects on those who had no socialist tendencies whatsoever. For example, it is Jack's wife who is believed to be the Communist but it is Jack who loses his job because of it.
Paranoia and Suspicion
There are several truly paranoid characters in the novel, the most extreme of whom is Joan Reiss, whose paranoia is so extreme that it actually provides an alternative reality for the other characters. This theme also extends to the primary McCarthyism theme, in that there was an enormous paranoia at the time about who was safe to be around and who was going to be hiding their left-wing tendencies.
Subjective Reality
This is one of the themes not only of this novel but of most of Dick's novels. His writing is preoccupied with the experiences of the individual and with whether everyone is experiencing actual reality or what they are being duped into thinking is reality This is most evident at the end of the novel when the author raises the question of whether the characters are now back in their own realities or merely players in other people's.
