Croire en vs Croire à

Question

Please help me explain why we use "en" in the sentence "elle ne pouvait pas en croire ses yeux !" Does it have anything to do with "Croire à vs Croire en"? Can I erase "en" in that sentence?

Cécile Janty-Davies · Accepted Answer

Hi Thanh Tân, 
There is a slight difference in meaning between 'croire à' et 'croire en' quelque chose.
Take a look at the explanation given by the Académie française -
https://www.academie-francaise.fr/l-de-l-allemagne
 
So you will say -

Julien croit encore au Père Noël = Julian still believes in Father Christmas
Ils croient aux fantômes = They believe in ghosts

but

Ils croient en Dieu = They believe in God
Ils croient en une amélioration de la situation financière = They believe in an improvement of the financial situation

and the set expression -
ne pas en croire ses yeux = to not believe your eyes

Jim Jones · Answer

Salut de nouveau Thanh Tân,If you look back to my input on your previous post, I think this current point has been covered?Bonne journéeJim