Existentialism In "Electric Sheep"

Existentialism, a sort of philosophical thinking, proposes that existence precedes essence, which means that things should at least exist in this world to have essence, or in other words, to become meaningful to the world. In the reality of "Electric sheep", different from ours, there lives a kind of human-made creatures, androids. Since it is debatable whether the existence of these human-like androids correspond to existentialism, existentialism becomes a crucial topic as the story proceeds.
Human beings, with self-consciousness, obtain its existence at the exact moment of birth. Subsequently, during the entire life, human's essence is unfirmed. Therefore, it's their own opportunity to discover their value to the world. Rick Deckard, a human leading character, work as a bounty hunter, alters his own essence little by little along with his meets with the androids. Though he was previously being defined as a ruthless bounty hunter to "retire" all of the escaped androids, he generates the feeling of empathy to the androids on his lists to kill and becomes reluctant to complete his paid job. His essence is changing according to his own free will, even continuously being deviated from his original one.
Unlike the human beings, the human-made androids live without the chance to change their essence or the social value, which are all predefined by genuine human and fixed without opportunity to be modified. Rachael Rosen, as an example of the androids, seems changing her attitude towards the issues all the time. However, through these changes, her essence is remained from the beginning to the end. Specifically, in chapter 4 and 5, her true features were revealed, before which she lived as a “human” professional in Rosen. After that, she surprisingly decided to assist Rick to “retire” other androids, since she has lost her value as a human but to continue her “life” span. These 2 distinct actions of Rachael, before and after the incident, share the same essence as to live like a human being.