Full Idea
It makes no sense to speak of comparing or agreeing on ultimate standards of rationality, since it is our own standards in each case to which we must turn in interpreting others. This is not a failure of objectivity, but where 'questions come to an end'.
Gist of Idea
There are no ultimate standards of rationality, since we only assess others by our own standard
Source
Donald Davidson (Davidson on himself [1994], p.232)
Book Reference
'A Companion to the Philosophy of Mind', ed/tr. Guttenplan,Samuel [Blackwell 1995], p.232
A Reaction
This seems wrong, given the commitment to truth and charity in interpretation. He could have said the same about perception, but I doubt if he would.