What is the universal theme of The Stranger?

Camus' novel is
expressive, primarily, of themes relating to absurdity and the difficulty of rendering life
meaningful. Mersault is a character who denies conventional and formal explanations of human
behavior. He does not see the same reasons for actions nor the same excuses for violence that
others do. 

In fact, Mersault sees a lack of reason in his most significant
act, a murder. When Mersault is captured and imprisoned, many people challenge him to accept
their explanations for his behavior. Lawyers and priests provide him with stories to excuse his
violence act. Mersault denies them all. 

In an expression
of Camuss humanist logic, neither theology nor fate can offer men of intelligence (men like
Meursault, willing to use only bare logic to consider the question of life) an explanation for
the absolutely senseless things that humans dowar, murder, and other heinous acts. The
alternative, therefore, is absurdity.

We can see from
early on in the novel that the world does not make sense to Mersault as it does to everyone
else. Another way to say this is that Mersault sees absurdity in the world, whereas others see
order, sense, and rationality. 

For Mersault, reason does not guides men's
behavior and certainly does not guide his own when he commits a murder. As a result of this lack
of reason, Mersault can draw very little meaning from the act. Where there is no reason and no
rationality, there is no meaning. 

Articulated as themes, these ideas of
absurdity and the difficulty of meaning can also be related to personal inability to construct a
meaningful worldview or philosophy. Mersault is a man beset with
absurdity.