“To be an artist at all is like living in Switzerland during a world war. To be an artist in Zurich, in 1917, implies a degree of self-absorption that would have glazed over the eyes of Narcissus.”

Source: Scar Tissue

The Scarlet Tree, Bk. IV, ch. 2.

Published as having been made in an (August 1936) interview http://www.greatwar.nl/frames/default-churchill.html with William Griffin, editor of the New York Enquirer http://en.wikipedia.org/wiki/National_Enquirer, who was indicted for sedition http://www.time.com/time/magazine/printout/0,8816,773366,00.html by F.D.R.'s http://www.whitehouse.gov/history/presidents/fr32.html Attorney General Francis Biddle http://www.usdoj.gov/osg/aboutosg/biddlebio.htm in 1942. In a sworn statement before Congress in 1939 Griffin affirmed Churchill had said this; Congressional Record (1939-10-21), vol. 84, p. 686. In 1942, Churchill admitted having had the 1936 interview but disavowed having made the statement (The New York Times, 1942-10-22, p. 13).
In his article "The Hidden Tyranny," Benjamin Freedman attributed this quotation to an article in the isolationist http://www.time.com/time/magazine/article/0,9171,795133,00.html publication Scribner's Commentator in 1936. However, that magazine did not exist until 1939. He may have gotten the date wrong or might have been referring to one of its predecessors, Scribner's Monthly http://cdl.library.cornell.edu/moa/browse.journals/scmo.html or Payson Publishing's The Commentator http://www.time.com/time/magazine/article/0,9171,765655,00.html.
Disputed

1960's, Conversations with Samuel Beckett and Bram van Velde' (1965 - 1969)

"Talk to an Art-Union (A Brooklyn fragment)" http://www.aol.bartleby.com/229/4011.html (1839); later delivered as a lecture at the Brooklyn Art Union (31 March 1851) and printed in the Brooklyn Daily Advertizer (3 April 1851)
Context: It is a beautiful truth that all men contain something of the artist in them. And perhaps it is the case that the greatest artists live and die, the world and themselves alike ignorant what they possess. Who would not mourn that an ample palace, of surpassingly graceful architecture, fill’d with luxuries, and embellish’d with fine pictures and sculpture, should stand cold and still and vacant, and never be known or enjoy’d by its owner? Would such a fact as this cause your sadness? Then be sad. For there is a palace, to which the courts of the most sumptuous kings are but a frivolous patch, and, though it is always waiting for them, not one of its owners ever enters there with any genuine sense of its grandeur and glory.
I think of few heroic actions, which cannot be traced to the artistical impulse. He who does great deeds, does them from his innate sensitiveness to moral beauty.

Source: Women in Love

On becoming an artist in “‘There’s No Diploma in the World That Declares You an Artist’: Watch Kara Walker Lay Out Her Advice for Art Students” https://news.artnet.com/art-world/watch-kara-walker-art-21-1316030 in artnetnews (2018 Jul 12)

The Future of Civilization (1938)
Context: During all the period before 1914, Europe and, in a degree, the whole world lived under the perpetual shadow of war, as we are doing, I am afraid, at the present time. No doubt after it had been going on for a certain time, people became callous. They thought war had been so often avoided that it would continue to be avoided. But nevertheless, all international policy was carried on on the basis that sooner or later war might and probably would have to be faced. This has again become true, and it casts its shadow over every form of human activity. The civil life of every nation is deformed and weakened and obstructed by this threat of war. We are wasting gigantic sums, sums far greater than we have ever wasted before, on preparations for war, because war has again become a very present possibility and, at the same time, its horrors and dangers are enormously greater than they were before 1914.

Un artiste n'est un artiste que grâce à son sens exquis du beau, — sens qui lui procure des jouissances enivrantes, mais qui en même temps implique, enferme un sens également exquis de toute difformité et de toute disproportion.
XI: "Notes nouvelles sur Edgar Poe III," IV http://fr.wikisource.org/wiki/Edgar_Poe_III._Notes_nouvelles_sur_Edgar_Poe_%28L%E2%80%99Art_romantique%29#IV
L'art romantique (1869)