Dick loved to write about the boundaries of humanity and how those boundaries are crossed or dissolved; with Do Androids Dream of Electric Sheep? (the source material for the movie), he wasn’t satisfied just talking about androids. He wanted to explore the mind of an android, how it would feel, what it would want — and whether humans would really know the difference. That ambiguity is perfectly suited to film noir, especially situated in a detective story, and coupled with Ridley Scott’s unforgettable science-fiction world-building (as well as the performances of Harrison Ford, Rutger Hauer, and the rest of the cast), it makes Blade Runner an undisputed classic.