How can we examine the movie Blade Runner in the view of the postmodernism?

Crucial to this excellent film version of Philip K. Dick's
novel, Do Androids Dream of Electric Sheep, is the central question
of identity and who we are. The film's major idea is the way in which replicants
(androids) and humans are completely identical. The only way that you are able to
distinguish between them is through an elaborate test that examines the eye and the
"blush response" when asked a series of questions. What makes the distinction between
humans and replicants even more complicated is the way that replicants have emotions and
can feel, and in the case of Rachel, have been "given" memories, so that they themselves
are unaware that they are replicants. The question that haunts the movie is whether
Dekkard himself is a replicant. How do we define humanity? What does it mean to be
human? These are key existential questions that haunt the film and its viewers long
after the film has finished.