Despite appearing to be an action film, Blade Runner has many dramatic, narrative levels, greatly indebted to film noir conventions, such as the femme fatale, protagonist-narration (removed in later versions), dark and shadowy cinematography, and the questionable moral outlook of the hero, extended to include his humanity.
It is a literate science fiction film, thematically enfolding the philosophy of religion and moral implications of human mastery of genetic engineering in the context of classical Greek drama and hubris, and draws on Biblical images, such as Noah's flood, and literary sources, such as Frankenstein. Linguistically, the theme of mortality is subtly reiterated in the chess game between Roy and Tyrell based on the famous Immortal game of 1851, though Scott has said that was coincidental.
Blade Runner delves into the implications of technology on the environment and society by reaching to the past, using literature, religious symbolism, classical dramatic themes, and film noir. This tension, among past, present, and future is seen in the retrofitted future of Blade Runner, which is high-tech and gleaming in places but elsewhere decayed and old. Interviewing Ridley Scott in 2002, reporter Lynn Barber in The Observer described the film as: "extremely dark, both literally and metaphorically, with an oddly masochistic feel". Director Scott said he "liked the idea of exploring pain" in the wake of his brother's skin cancer death. "When he was ill, I used to go and visit him in London, and that was really traumatic for me."
A perceptively high level of paranoia exists in the cinematic manifestation of corporate power, omnipresent police, probing lights, and in the power over the individual—especially represented by genetic programming of replicants. Control over the environment is large scale, hand in hand with the absence of any natural life, and with artificial animals substituting for the extinct originals. This oppressive backdrop clarifies why people are migrating to off-world colonies. The dystopian themes explored in "Blade Runner" are an early example of cyberpunk concepts expanding into film. The film also makes extensive use of eyes for a variety of themes and manipulated images to call into question reality and our ability to accurately perceive and remember it.
These thematic elements provide an atmosphere of uncertainty for Blade Runner's central theme of examining humanity. In order to discover replicants, an empathy test is used with a number of questions focused on the treatment of animals, thus making it the essential indicator of someone's "humanity". The replicants are juxtaposed with human characters who lack empathy, while the replicants appear to show compassion and concern for one another at the same time as the mass of humanity on the streets is cold and impersonal. The film goes so far as to put in doubt whether Deckard is a human, and forces the audience to reevaluate what it means to be human.
The question of whether Deckard is intended to be a human or a replicant has been an ongoing controversy since the film's release. Both Michael Deeley and Harrison Ford wanted Deckard to be human while Hampton Fancher preferred ambiguity. Ridley Scott has confirmed that in his vision Deckard is a replicant. Deckard's unicorn dream sequence inserted into the Director's Cut coinciding with Gaff's parting-gift of an origami unicorn is seen by many as showing Deckard is a replicant as Gaff could have access to Deckard's implanted memories.
The interpretation that Deckard is a replicant is challenged by others who believe unicorn imagery shows that the characters, whether human or replicant, share the same dreams and recognise their affinity, or that the absence of a decisive answer is crucial to the film's main theme. The inherent ambiguity and uncertainty of the film, as well as its textual richness, has permitted viewers to see it from their own perspective.