Analysis of Reason

... Finally, what is Reason ? You have often asked me ; and this is my
answer :--

Whene'er the mist, that stands 'twixt God and thee,
     [Sublimates] to a pure transparency,
     That intercepts no light and adds no stain--
     There Reason is, and then begins her reign !

But alas !
          ------`tu stesso, ti fai grosso
          Col falso immaginar, sì che non vedi
          Ciò che vedresti, se l'avessi scosso.'

(Dante, Paradiso, Canto 1, lines 88-90)