Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it’s the only thing that ever has.
There's no known primary source for this powerful quote, but it’s important to note it has never been attributed to anyone else. The Yale Book of Quotations says "Attributed in the Christian Science Monitor, 1 June 1989." I haven’t been able to track down this publication, so whether to not she said it in passing is difficult to say. The earliest attribution “is Earth at omega: passage to planetization” published a few years after her death by Donald Keys.