This provides an atmosphere of uncertainty for "Blade Runner's" central theme of examining humanity. In order to discover replicants, a psychological test is used with a number of questions intended to provoke emotion; making it the essential indicator of someone's "humanity". The replicants are juxtaposed with human characters who are unempathetic, and while the replicants show passion and concern for one another, the mass of humanity on the streets is cold and impersonal. The film goes so far as to put in doubt the nature of Rick Deckard and forces the audience to reevaluate what it means to be human.