Clare Boothe Luce (1903-1987), an American author and ambassador, addressed an IBM Golden Circle conference in Honolulu, Hawaii, on May 28, 1978:
 
“Above all, he is courageous. Courage is the ladder on which all the other virtues mount. Plautus, a true nobleman of antiquity, wrote, ‘Courage is what stands before everything. It is what preserves our liberty, our lives, our homes, and our parents, our children, our children, and our country. A man with courage has every blessing.’”
 
“Courage is the ladder on which all the other virtues mount” is a popular quotation that has been frequently included in quotation lists.
 
   
Wikipedia: Clare Boothe Luce
Clare Boothe Luce (March 10, 1903 – October 9, 1987) was the first American woman appointed to a major ambassadorial post abroad. A versatile author, she is best known for her 1936 hit play The Women, which had an all-female cast. Her writings extended from drama and screen scenarios to fiction, journalism, and war reportage. She was the wife of Henry Luce, publisher of Time, Life and Fortune.
 
14 March 1939, Arizona Republic (Phoenix, AZ), “Everyday Poems” by George Elliston, sec. 2, pg. 8, col. 3:
COURAGE A LADDER
My courage is a ladder on
Which I mount up and up.
The stars my goal on one of them,
At last I hope to sup.
 
Google Books
The Human Life Review
Volume 4
1978
Pg. 7:
Above all, he is courageous. Courage is the ladder on which all the other virtues mount. Plautus, a true nobleman of antiquity, wrote, “Courage is what stands before everything. It is what preserves our liberty, our lives, our homes, and our parents, our children, our children, and our country. A man with courage has every blessing.”
 
Google News Archive
19 July 1979, Spokane (WA) Daily Chronicle, “Shop with Sue,” pg. 5, col. 8:
Courage is the ladder on which all the other virtues mount.
 
Google News Archive
13 September 1979, Evening Independent (St. Petersburg, FL), “Bridge: Take Risks TO Make Bid” by Jeanne Truck, pg. 10-B, col. 5:
Remember that courage is a ladder that you must mount, if you would succeed!
 
10 April 1990, Ironwood (MI) Daily Globe, pg. 8, col. 4:
TODAY’S QUOTE: “Courage is the ladder on which all the other virtues mount.” - Clare Boothe Luce
 
Google Books
Landmark Speeches of the American Conservative Movement
Edited by Peter Schweizer and Wynton C. Hall
College Station, TX: Texas A & M University Press
2007
Pg. 55:
Clare Boothe Luce
“Is the New Morality Destroying America?”
May 28, 1978
Toward a Moral Renaissance
Pg. 57:
Delivered May 28, 1978, in Honolulu, Hawaii
I was honored—as who would not be?—by the invitation to address this Golden Circle of remarkable IBM achievers.
Pg. 61:
Above all, he is courageous. Courage is the ladder on which all the other virtues mount. Plautus, a true nobleman of antiquity, wrote, “Courage is what stands before everything. It is what preserves our liberty, our lives, our homes, and our parents, our children, our children, and our country. A man with courage has every blessing.”
 
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Carrie Wilkerson
‏@CarrieWilkerson  
“Courage is the ladder on which all the other virtues mount.”  Clare Booth Luce - from http://powerlinesforwomen.com
7:04 AM - 17 Sep 08