Comment on the significance of the title Do Androids Dream of Electric Sheep?

The central theme of this excellent work, which was, of
course, made into the film Bladerunner starring Harrison Ford, is
the nature of humanity. What makes us human? And in particular, when we are in a world
populated by humans and androids who resemble humans so perfectly and even have emotions
and are given their own past, like Rachel, what separates us from androids? We, as
humans, are able to dream of one day having possessions or reaching positions of
happiness and contentment, but are androids able to have similar dreams, just as Deckard
dreams of having his own electric sheep? And if they are, what really does make us
different from artificially formed life?

Thus the question
of the title goes to the heart of the theme of humanity in the play and how we define
it. Throughout it all, the worrying notion of Deckard himself being a replicant
questions our own basis of how we define ourselves and severely limits the sense in
which we can consider ourselves to be unique.