The most dangerous untruths are truths slightly distorted.
— G. C. (Georg Christoph) Lichtenberg

A new untruth is better than an old truth.
Oliver Wendell Holmes untruth quote

In the second half of life the necessity is imposed of recognizing no longer the validity of our former ideals but of their contraries. Of perceiving the error in what was previously our conviction, of sensing the untruth in what was our truth, and of weighing the degree of opposition, and even of hostility, in what we took to be love.
— Carl Jung

A belief, however necessary it may be for the preservation of a species, has nothing to do with truth. The falseness of a judgment is not for us necessarily an objection to a judgment. The question is to what extent it is life-promoting, life-preserving, species preserving, perhaps even species cultivating. To recognize untruth as a condition of life--that certainly means resisting accustomed value feelings in a dangerous way; and a philosophy that risks this would by that token alone place itself beyond good and evil.
— Friedrich Nietzsche

One of the most untruthful things possible, you know, is a collection of facts, because they can be made to appear so many different ways.
— untruth quotation by Karl Menninger