“There is no truth but untruth. There is no reason but unreason.”

H 7
Variant translation: The most dangerous untruths are truths slightly distorted.
Aphorisms (1765-1799), Notebook H (1784-1788)

The Overman Culture (1971)

Part Two: 2. The Transcendence of Delirium
History of Madness (1961)
Context: To say that madness is dazzlement is to say that the madman sees the day, the same day that rational men see, as both live in the same light, but that when looking at that very light, nothing else and nothing in it, he sees it as nothing but emptiness, night and nothingness. Darkness for him is another way of seeing the day. Which means that in looking at the night and the nothingness of the night, he does not see at all. And that in the belief that he sees, he allows the fantasies of his imagination and the people of his nights to come to him as realities. For that reason, delirium and dazzlement exist in a relation that is the essence of madness, just as truth and clarity, in their fundamental relation, are constitutive of classical reason.
In that sense, the Cartesian progression of doubt is clearly the great exorcism of madness. Descartes closes his eyes and ears the better to see the true light of the essential day, thereby ensuring that he will not suffer the dazzlement of the mad, who open their eyes and only see night, and not seeing at all, believe that they see things when they imagine them. In the uniform clarity of his closed senses, Descartes has broken with all possible fascination, and if he sees, he knows he really sees what he is seeing. Whereas in the madman’s gaze, drunk on the light that is night, images rise up and multiply, beyond any possible self-criticism, since the madman sees them, but irremediably separated from being, since the madman sees nothing.
Unreason is to reason as dazzlement is to daylight.

"The Prevention of Literature" (1946)
Context: The enemies of intellectual liberty always try to present their case as a plea for discipline versus individualism. The issue truth-versus-untruth is as far as possible kept in the background. Although the point of emphasis may vary, the writer who refuses to sell his opinions is always branded as a mere egoist. He is accused, that is, either of wanting to shut himself up in an ivory tower, or of making an exhibitionist display of his own personality, or of resisting the inevitable current of history in an attempt to cling to unjustified privileges.

Source: 1984

Harijan (13 July 1947) p. 232
1940s

Source: Culture and Value (1980), p. 41e

Source: Personal Destinies: A Philosophy of Ethical Individualism (1976), p. 8

Pt. VIII, ch. 13
Source: Anna Karenina (1875–1877; 1878)
Context: Reason has discovered the struggle for existence and the law that I must throttle all those who hinder the satisfaction of my desires. That is the deduction reason makes. But the law of loving others could not be discovered by reason, because it is unreasonable.