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.
Video: Blade Runner Classic
Although Blade Runner is ostensibly an action film, it operates on multiple dramatic and narrative levels. It is indebted to film noir conventions: the femme fatale; protagonist-narration (removed in later versions); dark and shadowy cinematography; and the questionable moral outlook of the hero – in this case, extended to include reflections upon the nature of his own 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.
It also 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.