system
Given the following post, respond as if you're commenting on Reddit:
human
How did Schopenhauer influence existentialism?

Schopenhauer believed that the noumenal, universal Will manifests itself in humans as lower-case will, and because the grand Will has no purpose/way to be satisfied is he saying that humans have no purpose/ultimate satisfaction? Is this how he lays the foundations for existentialism?
gpt
It's less that Schopenhauer himself was an immediate influence on existentialism as much as that he was an immediate influence on a philosopher who was an immediate influence on existentialism: Friedrich Nietzsche. And it's not quite right to describe Nietzsche as merely influenced by Schopenhauer's philosophy as Nietzsche's philosophy, in  very real ways, was a continuation, correction, and repudiation of aspects of Schopenhauer's philosophy. 

Whereas Schopenhauer saw will to live as the driving force of all living things and, as inspired by Buddhism (though important to note *not* the view of Buddhism wrt nirvana), called for a denial of the will; Nietzsche saw the will to power as the driving force of all living things and called for an affirmation of life and will. 

It's this register of affirmation in the face of suffering, doubt, freedom, the absurd, etc. that existentialism comes out of. Existentialism is, in an indirect way, a response to Schopenhauer's pessimism.