In the end, what are man’s truths? His irrefutable errors.

[Was sind denn zuletzt die Wahrheiten des Menschen? — Es sind die unwiderlegbaren Irrthümer des Menschen.]

Friedrich Nietzsche (1844-1900) German philosopher and poet

The Gay Science [Die fröhliche Wissenschaft], Book 3, § 265 (1882) [tr. Hill (2018)]
    (Source)

Also known as La Gaya Scienza, The Joyful Wisdom, or The Joyous Science.

(Source (German)). Alternate translations:

But what after all are man's truths? -- They are his irrefutable errors.
[tr. Common (1911)]

What are man's truths ultimately? Merely his irrefutable errors.
[tr. Kaufmann (1974)]

What, then, are man's truths ultimately? -- They are the irrefutable errors of man.
[tr. Nauckhoff (2001)]