Historical clue formulations

• Ability to think rationally — 2022-11-28
• "___ and happiness are an impossible combination": Mark Twain — 2018-10-19
• "A cozy lie," per Susan Sontag — 2015-03-06
• "Madness put to good uses," per George Santayana — 2013-01-24
• Levelheadedness — 2012-05-11
• Reasonableness — 2006-05-02
• Sensibleness — 2004-11-23
• Soundness of mind — 2003-10-06
• Marbles, so to speak — 2003-01-08
• Balance — 2000-11-29
• Marbles, so to speak — 1996-03-03