“To love truth for truth's sake is the principal part of human perfection in this world, and the seed-plot of all other virtues.”
Letter to Anthony Collins (29 October 1703) http://oll.libertyfund.org/titles/1726#lf0128-09_head_098
Help us to complete the source, original and additional information
John Locke 144
English philosopher and physician 1632–1704Related quotes

Book IV, Ch. 19 : Of Enthusiasm (Chapter added in the fourth edition).
Variant paraphrase, sometimes cited as a direct quote: One unerring mark of the love of truth is not entertaining any proposition with greater assurance than the proofs it is built upon will warrant.
As paraphrased in Peter's Quotations : Ideas for our Time (1979) by Laurence J. Peter, p. 500; also in The Demon-Haunted World : Science as a Candle in the Dark (1994) by Carl Sagan, p. 64
An Essay Concerning Human Understanding (1689)
Context: He that would seriously set upon the search of truth, ought in the first place to prepare his mind with a love of it. For he that loves it not, will not take much pains to get it; nor be much concerned when he misses it. There is nobody in the commonwealth of learning who does not profess himself a lover of truth: and there is not a rational creature that would not take it amiss to be thought otherwise of. And yet, for all this, one may truly say, that there are very few lovers of truth, for truth's sake, even amongst those who persuade themselves that they are so. How a man may know whether he be so in earnest, is worth inquiry: and I think there is one unerring mark of it, viz. The not entertaining any proposition with greater assurance than the proofs it is built upon will warrant. Whoever goes beyond this measure of assent, it is plain receives not the truth in the love of it; loves not truth for truth's sake, but for some other bye-end.

In Encyclical Letter Spe Salvi http://www.vatican.va/holy_father/benedict_xvi/encyclicals/documents/hf_ben-xvi_enc_20071130_spe-salvi_en.html (30 November 2007)
2007

“Only on paper has humanity yet achieved glory, beauty, truth, knowledge, virtue, and abiding love.”

“I believe Beauty is the condition of the perfect life, just as important as Virtue and Truth.”
"Credo"

Notes, 1962; as cited on collected quotes on the website of Gerhard Richter: 'on Art' https://www.gerhard-richter.com/en/quotes/art-1
1960's

Introduction.
Race and Democratic Society (1945)

1920s, The Prospects of Industrial Civilization (1923)
Context: The governors of the world believe, and have always believed, that virtue can only be taught by teaching falsehood, and that any man who knew the truth would be wicked. I disbelieve this, absolutely and entirely. I believe that love of truth is the basis of all real virtue, and that virtues based upon lies can only do harm.