Blade Runner

Blade Runner, Frankenstein and R.U.R. are very similar in that they all create artificial life in human image only to exploit their life. Humans are made in God's image and man is copying that image in those stories. Why don't the scientists create a new life in their eyes, why is it always under God's image? Its because man is selfish so the human image is what is comfortable to us. There has to be a more efficient design than the human design, for example the uselessness of an appendix or other minor evolutionary errors. This is why the robots/creatures revolt, they look, act, and feel what humans do but are treated as lessors.

Roy let Deckard live because Deckard is a replicant himself. There are many suggestions through out the movie such as how emotionless Deckard can be or Roy's remark of them having the same eyes. He also developes more emotions through the length of the film such as love. Rachel the female replicant did not know she was a replicant either so that means Deckard could be a "special" replicant also. Deckards purpose could have been to fight rogue replicants in a fire versus fire manner since the replicants were faster and stronger than humans. Just as Frankenstein did not know that his science was impossible because no one told him, it allowed him to achieve the impossible. Deckard's strength and speed would look human only because he believed he was human so he acted human. By acting human and believing he was human it allowed him to have faith and love among many other human characteristics that the other replicants did not acquire.