Each of the renegades were created to the newest technological level possible, and their creator challenges Deckard to distinguish his new models from a human by using Rachel (Sean Young) as an example of the level of humanity he has accomplished in his humanoid design. Deckard finds his self strangely attracted to Rachel in a very human way, and she responds to his emotions, sensing his feelings, and returning those emotions. Deckard faces a moral dilemma. Of course, in the end, the Replicants (robots) manifest their creator's dark side, and kill to survive.

That they are artificial life forms should erase the doubt of whether or not...

The impetus of their creation was to serve humans. However, in the film, Deckard is challenged with the idea that he himself might be a Replicant, and finds himself questioning his own human memories and instincts. He is, of course, very human, and it is his instincts as to what he senses about the Replicants that leads him to be a good Replicant hunter. It is the emotional breadth Deckard possesses over the Replicants that distinguish him as human, and they as replicated human forms.
Reference List

Scott, R. (1982). Blade Runner, motion picture, Ladd Company, USA.