“Revolution is never going to finish, because we can never stop reforming our democracy. The moment the revolution stops means the revolution has been betrayed.”

Address delivered before the Twenty-Eighth Congregational Society in Music Hall, Boston, February 17, 1861, published in Speeches, Letters and Lectures by Wendell Phillips https://archive.org/details/speecheslectures7056phil (1884), p. 380.
1860s

Source: Hainish Cycle, (1974), Chapter 12 (p. 359)

Speech, San Francisco, California (9 September 1952)

Interview with Oriana Fallaci (2 December 1979), Corriere della Sera
Interviews

The School for Dictators http://books.google.com/books?id=9scdAAAAMAAJ&q=%22Fascism+was+a+counter-revolution+against+a+revolution+that+never+took+place%22&pg=PA42#v=onepage (1938)

Words to Intellectuals (1961)

This fact must be grasped first and foremost: unless it is understood, we cannot advance. We must know how to supplement and amend old "formulas".
Lenin Anthology, p. 301
1910s, "The Dual Power" (1917)

Alan Moore on Anarchism (2009)
Context: I don’t believe that a violent revolution is ever going to work, simply on the grounds that it never has in the past. I mean, speaking as a resident of Northampton, during the English civil war we backed Cromwell — we provided all the boots for his army — and we were a center of antiroyalist sentiment. Incidentally, we provided all the boots to the Confederates as well, so obviously we know how to pick a winner. Cromwell’s revolution? I guess it succeeded. The king was beheaded, which was quite early in the day for beheading; amongst the European monarchy, I think we can claim to have kicked off that trend. But give it another ten years; as it turned out, Cromwell himself was a monster. He was every bit the monster that Charles I had been. In some ways he was worse.