الأخطاء هي، بعد كل شيء، أساسات الحقيقة، وإذا كان الرجل لا يعرف ما هو الشيء، فإنه على الأقل زيادة في المعرفة إذا كان يعرف ما هو ليس.

These are genuinely Jung's words. The line comes from his essay "Psychological Aspects of the Mother Archetype," collected in Volume 9, Part 1 of the Collected Works (The Archetypes and the Collective Unconscious), where in R. F. C. Hull's translation it appears at paragraph 79, amid Jung's discussion of how hard it is to separate archetypal projection from empirical reality. We confirmed the wording against Jung's German original ("Irrtümer bildeten schließlich meist die Fundamente der Wahrheit..."), which settles that this is an authentic translated Jung sentence rather than a loose English paraphrase, and we found the exact English text reproduced in scholarly compilations of Jung, including Jolande Jacobi's Psychological Reflections and the Columbia Dictionary of Quotations. A handful of popular collections misfile it under Jung's Aion (1951), but the essay text and the German source both point to the Mother Archetype essay as its true home. We also tested and dismissed a claim that George Bernard Shaw wrote the line first: no Shaw work actually contains it, and the versions floated under his name were inconsistent and traced only to unattributed quote lists—so there is no competing origin and no evidence it predates Jung.