Full Idea
In Plato's theory, to be rational is to have a vision of rational order, and to love this order.
Gist of Idea
For Plato, rationality is a vision of and love of a cosmic rational order
Source
report of Plato (The Republic [c.374 BCE], 537d) by Charles Taylor - Sources of the Self §4.1
Book Reference
Taylor,Charles: 'Sources of the Self' [CUP 1992], p.92
A Reaction
There may be a worrying elitism in this, but it helps to pinpoint the sense in which 'all philosophers are Platonists'.