“A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.”

Source: Bitter Angels (2009), Chapter 9 (p. 124)

Source: On Building Systems That Will Fail (1991), p. 75

[Tilove, Jonathan, Beto Effin’ O’Rourke: On running for Senate with the expletive undeleted First Reading, http://politics.blog.mystatesman.com/2017/09/25/beto-effin-orourke-on-running-for-senate-with-the-expletive-undeleted/, My Statesman, 12 November 2018, en, September 25, 2017] When asked about his "youthful indiscretions"
2017

Source: The Master and Margarita

Virlomi.
Ender's Game series, Shadow of the Giant (2005)

Oglethorpe University Commencement Address http://publicpolicy.pepperdine.edu/academics/faculty/lloyd/projects/newdeal/fr052232.htm (22 May 1932)
1930s
Context: The country needs and, unless I mistake its temper, the country demands bold, persistent experimentation. It is common sense to take a method and try it: If it fails, admit it frankly and try another. But above all, try something. The millions who are in want will not stand by silently forever while the things to satisfy their needs are within easy reach. We need enthusiasm, imagination and the ability to face facts, even unpleasant ones, bravely. We need to correct, by drastic means if necessary, the faults in our economic system from which we now suffer. We need the courage of the young. Yours is not the task of making your way in the world, but the task of remaking the world which you will find before you. May every one of us be granted the courage, the faith and the vision to give the best that is in us to that remaking!