[lobster_johnson]

In the novel, Deckard considers that he might be an android; he encounters a man who suspects he's not human, and even encounters an entire fake police force. But he isn't, and the point of the novel would be less effective if he were.

A major theme in the novel is the idea that there's a significant difference between the real and the fake. The major characters are depressed, stuck in a world where almost all animals are fake, and there are even fake humans. In the novel, Rachael and the other androids do not have empathy; she throws his sheep off the roof of his building as revenge. The point of Deckard's mission (unlike the movie) isn't necessarily to show us that androids' lives also matter, it's to contrast the fake humans with the all-to-human Deckard. (This part is something of a gray area since we're only told that the Voigt-Kampff test works.)

But it's also true that the movie doesn't really make sense if Deckard is a replicant. First of all, he would be a pitiful replicant; he barely survives his encounter with them, and has none of their superhuman skills. But that's a technical point. But if he is a replicant, the movie has no arc -- it's the story about a guy who kills some replicants and maybe (we don't know) realizes that he himself is a replicant and has four years to live. It's not clever, and provides no emotional resonance.

But if Deckard is human, then it's a story about a man, trained to kill replicants, who learns the value of life, even if it's not natural life. In the movie, despite the existence of the Voigt-Kampff test, the replicants clearly have empathy -- Roy mourning Pris' death is an example. So Deckard, it can be argued, is a bad guy in the movie; he's killing living beings who were designed to be slaves and have escaped from their masters. And the movie is about how, in his pursuit of the replicants, is himself made to be hunted, and learns what it is like to be like (but not actually be) a replicant.

Thematically, the Deckard-is-human interpretation is much more resonant than the Deckard-is-a-replicant interpretation.

[sbmassey]

I'd say the movie was more about Roy Batty and his chums falling from Heaven to Earth, Roy meeting their creator and then killing him, and then sparing their tormentor while dying. The "Deckard learns what it is to be hunted" theme doesn't seem to work as he's mostly doing a bunch of hokey detective work, punctuated by fairly evenly matched violence whenever he actually encounters a replicant - to make the theme work you would need to depict him tormenting innocent replicants in the same way Roy would later do to him.

In addition, I don't think the replicants are meant to be without empathy, as much as having a skewed sense of empathy compared to normal humans - Rachel is detected after not distinguishing between eating oysters and boiled dog, for instance.