Full Idea
Justifications come to an end when we are content to have them end.
Gist of Idea
Justifications come to an end when we want them to
Source
Thomas Nagel (The Absurd [1971], §3)
Book Reference
Nagel,Thomas: 'Mortal Questions' [CUP 1981], p.16
A Reaction
This is the correct account, with the vital proviso that where justification comes to an end is usually a social matter. Robinson Crusoe doesn't care whether he 'knows' - he just acts on his beliefs.