A pessimistic philosopher, Schopenhauer is known to have opposed the optimistic ideas emphasized by the German idealists of the 19th century such as Fichte, Shelling, and Hegel. His approach was different from the tradition of the metaphysics of reason that had been more prevalent since Kant`s The Critique of Pure Reason because he suggested that the will-to-live should be substituted for reason, corresponding to Kant`s thing-in-itself or Plato`s form. Especially sexual will, to his eyes, reveals the innermost essence of everything in nature as one of the most strengthened instincts, whose causal nature is not etiologically explicable, creating not a little hostility among intellectuals. Given this, we draw a distinction between reason and sexual will by referring to Schopenhauer`s philosophical theory and illuminate what aspects sexual will shows to reason by observing Robinson Jeffers`s "Roan Stallion" and John Steinbeck`s four short stories "The Snake," "The Chrysanthemums," "The White Quail," and "The Harness." This analysis shows how, in "Roan Stallion," the heroine California experiences an initiation process where she finds her real sexual will by an act of bestiality. Meanwhile, "The Snake" and "The Chrysanthemums" depict situations where sexual will bursts forth in the space controlled by reason in the name of cold practicality and science. Also, "The White Quail" and "The Harness" show the appearance that sexual will repressed by the power of reason gives the characters suffering and agony. Lastly, Schopenhauer`s theory of sexual will is found to account for irrational human acts behind reason and to emphasize a sort of asceticism by acknowledging and looking to its destructive power.