“I could not think of any human behaviour which could not be interpreted in terms of either theory. It was precisely this fact — that they always fitted, that they were always confirmed — which in the eyes of their admirers constituted the strongest argument in favour of these theories. It began to dawn on me that this apparent strength was in fact their weakness.”

The earliest published attribution of this quote to Einstein found on Google Books is the 1991 book The Art of Computer Systems Performance Analysis by Raj Jain (p. 507), but no source to Einstein's original writings is given and the quote itself is older; for example New Guard: Volume 5, Issue 3 from 1961 says on p. 312 http://books.google.com/books?id=5BbZAAAAMAAJ&q=%22fit+the+theory%22#search_anchor "Someone once said that if the facts do not fit the theory, then the facts must be changed", while Product engineering: Volume 29, Issues 9-12 from 1958 gives the slight variant on p. 9 "There is an age-old adage, 'If the facts don't fit the theory, change the theory.' But too often it's easier to keep the theory and change the facts." These quotes are themselves probably variants of an even earlier saying which used the phrasing "so much the worse for the facts", many examples of which can be seen in this search http://www.google.com/search?tbo=p&tbm=bks&q=facts+fit+%22so+much+the+worse+for+the+facts%22&tbs=,cdr:1,cd_max:Dec%2031_2%201950&num=10; for example, the 1851 American Whig Review, Volumes 13-14 says on p. 488 http://books.google.com/books?id=910CAAAAIAAJ&pg=PA488#v=onepage&q&f=false "However, Mr. Newhall may possibly have been of that casuist's opinion, who, when told that the facts of the matter did not bear out his hypothesis, said 'So much the worse for the facts.'" The German idealist philosopher Johann Gottlieb Fichte circa 1800 did say "If theory conflicts with the facts, so much the worse for the facts." The Hungarian Marxist Georg Lukacs in his "Tactics and Ethics" (1923) echoed the same quotation.
Misattributed

I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.
"Evolution as Fact and Theory", pp. 254–55 (originally appeared in Discover Magazine, May 1981)
Hen's Teeth and Horse's Toes (1983)

Source: The Mysterious Affair at Styles (1920)

Source: Dynamics in Psychology, 1940, p. 55

Pg. 33.
Against Method (1975)

"Legislators of the world" in The Guardian (18 November 2006)
Context: Of course, like the consciousness behind it, behind any art, a poem can be deep or shallow, glib or visionary, prescient or stuck in an already lagging trendiness. What's pushing the grammar and syntax, the sounds, the images — is it the constriction of literalism, fundamentalism, professionalism — a stunted language? Or is it the great muscle of metaphor, drawing strength from resemblance in difference? Poetry has the capacity to remind us of something we are forbidden to see. A forgotten future: a still uncreated site whose moral architecture is founded not on ownership and dispossession, the subjection of women, outcast and tribe, but on the continuous redefining of freedom — that word now held under house arrest by the rhetoric of the "free" market. This on-going future, written-off over and over, is still within view. All over the world its paths are being rediscovered and reinvented.
There is always that in poetry which will not be grasped, which cannot be described, which survives our ardent attention, our critical theories, our late-night arguments. There is always (I am quoting the poet/translator Américo Ferrari|) "an unspeakable where, perhaps, the nucleus of the living relation between the poem and the world resides".

Introduction à l'Étude de la Médecine Expérimentale (1865)

Source: An Essay on The Principle of Population (First Edition 1798, unrevised), Chapter I, paragraph 9, lines 1-2

Less Liberté Means Less Egalité http://www.city-journal.org/html/16_1_sndgs05.html (Winter 2006).
City Journal (1998 - 2008)