The ethical path Schopenhauer prescribes — quietism, asceticism, resignation — runs directly against the demands of biological life. To deny the will is not to commit suicide, which would merely be one more act of the will; it is to refuse the will's deepest demands: the drives of sexuality, self-preservation, and the hunger for more. The great mystics and saints of every tradition — Hindu renunciants, Christian ascetics, Buddhist monks — are, for Schopenhauer, the highest human types: they have broken the cycle not through negation but through the penetrating knowledge that individual selfhood is illusory and the will that animates it is the source of all suffering.
The path from ordinary moral life to ascetic denial passes through compassion. To feel genuine compassion — to experience another's suffering as one's own — is to penetrate the principium individuationis, the veil of individuation that makes each person appear as a separate being. The compassionate person has already, at an emotional level, grasped what the philosopher grasps conceptually: that the distinction between self and other is a feature of representation, not of the underlying reality. Every other person's suffering is, at the level of the will, my suffering.
Schopenhauer recognised in Buddhism — which he encountered relatively late but embraced enthusiastically — a philosophical tradition that had arrived at the same conclusions through a different path. The Buddhist diagnosis of suffering as rooted in craving (tanha), the ideal of nirvana as the extinction of desire, the metaphysical claim that individual selfhood is illusory (anatta) — all of these find precise analogues in his own system. He did not claim direct influence in either direction, but regarded the convergence as confirmation that both traditions had arrived, independently, at the deepest truths about human existence.
The Fourth Book of The World as Will and Representation (§55–71) presents Schopenhauer's ethics and the doctrine of the denial of the will. His affinity with Buddhist philosophy is noted throughout §68–71 and explored at greater length in Parerga and Paralipomena.