Existence Precedes Essence

Jean Paul Sartre developed the philosophical idea that our existence, our being, precedes our essence, or our meaning. Every human being alive begins by simply existing, but it is through our actions that we truly define ourselves.
The Universe is constantly acting on us. Every moment, we are being pushed and pulled by thousands of outside forces. For many of us, it is easy to simply let the world carry us through life in a mindless trance. We wake up, eat, work, sleep, and repeat. We never cease existing, but are we living? The moment that we begin to think and act for ourselves is the moment that we bring about our true essence.
In regards to "The Stranger," Mersault is a prime example of a person living without essence. He allows the Universe to act on him, but never takes these actions into ownership. From the outside looking in, it seems as though Mersault is living a typical, satisfying life. He works, he grieves, he befriends, he marries. But the inner-monologue that the novel gives us access to tells a very different story. There is detachment in every word. He works because he needs to sustain a job to support himself. He grieves because that is what is expected of someone who has just lost their mother. He befriends because others befriend him. He marries simply because a woman asks him to. He exists because existence was granted to him.
However, things take a drastic turn at the novel's midpoint. In the midst of a climactic fight, Mersualt is given a choice: to die or to kill. For the first time, he takes his life into his own hands and makes a choice that veers away from the simple routine and threatens to drag him into the thing he has so long avoided: essence.