“You're truly free for the first time. What could be more difficult than that?”

As quoted in obituaries (5 November 1954)
1950s

Letter to Camille Desmoulins (1792-06-24) in Œuvres de Desmoulins p. 76ff

Natural Philosophy of Time (1980) as quoted by Suk-Jun Kim, "Time felt and places imagined in my compositions" (2011)
Context: Although the peculiarly fundamental nature of time in relation to ourselves is evident as soon as we reflect that our judgments concerning time and events in time appear themselves to be 'in' time, whereas our judgments concerning space do not appear themselves in any obvious sense to be in space, physicists have been influenced far more profoundly by the fact that space seems to be presented to us all of a piece, whereas time comes to us only bit by bit. The past must be recalled by the dubious aid of memory, the future is hidden from us, and only the present is directly experienced. This striking dissimilarity between space and time has nowhere had a greater influence than in physical science based on the concept of measurement. Free mobility in space leads to the idea of the transportable unit length and the rigid measuring rod. The absence of free mobility in time makes it much more difficult for us to be sure that a process takes the same time whenever it is repeated.

Source: So Long, and Thanks for All the Fish

Il est plus facile d'être amant que mari, par la raison qu'il est plus difficile d'avoir de l'esprit tous les jours que de dire de jolies choses de temps en temps.
Part I, Meditation V: Of the Predestined, aphorism LXIX.
Physiology of Marriage (1829)

How Children Learn (1967).

Hays translation
Source: Meditations (c. AD 121–180), Book IV, 32

Free Speech in Wartime (October 6, 1917)

Interview on Middle East Television Network, February 18, 2004 http://georgewbush-whitehouse.archives.gov/news/releases/2004/02/20040218-10.html
2000s, 2004