Full Idea
I propose that the only criterion for what is a fact is what it is rational to accept.
Gist of Idea
A fact is simply what it is rational to accept
Source
Hilary Putnam (Reason, Truth and History [1981], Pref)
Book Reference
Putnam,Hilary: 'Reason, Truth and History' [CUP 1998], p.-3
A Reaction
An epistemological-ontological confusion here. The concept of a fact is of something which is the case quite independently of our criteria for believing it. There are facts which are unknowable for humans. It is, of course, rational to accept facts.