Question

Which was not a belief of Voltaire?

Answer 1

Answer; 
Life is short, nasty, and "brutish". 
This was not a belief of Voltaire.

Explanation;
Voltaire did not believe in any single religion, and also he never believe that one was needed to believe in God.
He was very much interested in the natural was that were underlying in all religions. Like most of Enlightenment thinkers, Voltaire considered himself a deist. 

Answer 2

Voltaire believed that the English system was better than the French, that God doesn't take part in human lives, and that Kings should be guided by reason. He did not believe that life is short, nasty, and "brutish."