Full Idea
All revolutions ...originate solely from the fact that spirit, in order to understand and comprehend itself with a view to possessing itself, has changed its categories, comprehending itself more truly, more deeply, more intimately in unity with itself.
Gist of Idea
All revolutions result from spirit changing its categories, to achieve a deeper understanding
Source
Georg W.F.Hegel (Philosophy of Nature (Encylopedia II) [1817], §246), quoted by Stephen Houlgate - An Introduction to Hegel 01
Book Reference
Houlgate,Stephen: 'An Introduction to Hegel' [Blackwell 2005], p.7
A Reaction
Some Hegelian waffle here, but it focuses on what seems important, which is how societal thinking has shifted, so that what was previously tolerated now triggers a revolution.