There are no dangerous thoughts, thinking itself is dangerous.
Hannah Arendt, "Thinking and Moral Considerations: A Lecture", Social Research, Vol. 38, No. 3 (Autumn 1971), p. 435
Alternate version: There are no dangerous thoughts for the simple reason that thinking itself is such a dangerous enterprise.
Interview with Roger Errera (October 1973), broadcast on Un Certain Regard (6 July 1974), ORTF TV, France. Published as "The Last Interview" in the Hannah Arendt Newsletter #2 (December 1999) and Hannah Arendt: The Last Interview and Other Conversations (Brooklyn: Melvin House, 2013).