In a word, a free government — that is, a government constantly subject to agitation — cannot last if it is not capable of being corrected by its own laws.

[En un mot, un gouvernement libre, c’est-à-dire toujours agité, ne saurait se maintenir s’il n’est, par ses propres lois, capable de correction.]

Charles-Lewis de Secondat, Baron de Montesquieu (1689–1755) French political philosopher

Considerations on the Causes of the Greatness of the Romans and their Decline [Considérations sur les causes de la grandeur des Romains et de leur décadence], ch. 8 (1734, 1748 ed.) [tr. Lowenthal (1965)]
    (Source)

(Source (French)). Other translations:

In a word, a free government, that is to say, one for ever in motion, cannot support itself, unless its own laws are capable of correcting the disorders of it.
[tr. B--- (1734)]

In a word, a free government -- that is to say, one which is constantly agitated -- can never maintain itself if it is not, by its own laws, capable of correction.
[tr. Baker (1882)]