Full Idea
My main argument can be fairly easily understood in terms of seeing rationality as conformity with reasons that one can sustain, even after scrutiny, and not just at first sight.
Gist of Idea
Rationality is conformity to reasons that can be sustained even after scrutiny
Source
Amartya Sen (The Idea of Justice [2009], 08 'Rational' n)
Book Reference
Sen, Amartya: 'The Idea of Justice' [Penguin 2010], p.180
A Reaction
We would need to say more about the 'scrutiny' before we had a really good account of rationality here. In Idea 20982 he emphasises the need for scrutiny by other people, and not mere self-criticism. The key may to be invite outside criticism.