“How old am I? Old enough to know it’s impossible to change the thinking of fools, but young and foolish enough to keep on trying.”
The New High Intensity Training (2004)
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Arthur Jones (inventor) 11
American inventor 1926–2007Related quotes

“Young men think old men are fools; but old men know young men are fools.”
Act V, scene i.
All Fools (1605)
On why young adult literature is so important in “Safer Is Not Always Better: An Interview With Stacey Lee” https://parnassusmusing.net/2019/08/13/interview-stacey-lee-downstairs-girl/ in Musing (2019 Aug 13)

“Old men are always young enough to learn.”
Variant translation: Learning is ever in the freshness of its youth, even for the old.
Source: Oresteia (458 BC), Agamemnon, line 584 ( line 583 of Richmond Lattimore's translation http://books.google.com/books?id=3duN7nP3OQYC&q=%22old+men+are+always+young+enough+to+learn%22&pg=PA40#v=onepage)

“And did you ever stop to think that im old enough to go to war but i aint old enough to drink.”

“I am not young enough to know everything.”
Variant: I am not young enough to know everything.

Source: The Foundation series (1951–1993), Foundation’s Edge (1982), Chapter 8 “Farmwoman” section 5, p. 154

"Repeal the 26th Amendment!" (10 November 2010) http://www.anncoulter.com/cgi-local/article.cgi?article=395.
2010
“Old enough to look as if he knew what to do, young enough to look as if he could do it.”
Source: The Tejano Conflict (2014), Chapter 4