Schopenhauer held that will is the source of all suffering.

Evidence

The cosmic will is wicked; will, altogether, is wicked, or at any rate is the source of all our endless suffering. Suffering is essential to all life, and is increased by every increase of knowledge. Will has no fixed end, which if achieved would bring contentment. — Bertrand Russell, History of Western Philosophy, 2739

Categorization

• DEFINE: Crisply states the pessimist thesis that will drives endless suffering.
• corroborated: 2 independent passages support this claim — Bertrand Russell, History of Western Philosophy, 2739
• XREF: connects to: Will-primacy doctrine, not pessimism, is Schopenhauer’s most influential legacy. — Bertrand Russell, History of Western Philosophy, 2752