“He could prove to wonderful effect that there was no effect without cause, and that, in this best of all possible worlds, His Lordship the Baron’s castle was the finest of castles and Her Ladyship the best of all possible baronesses.” 

Pangloss’ assertion that they live in the “best of all possible worlds” frames Candide’s understanding of the world while he lives with the Baron and Baroness and guides him throughout his journey. It is one he innocently accepts and later must question with each tragic encounter abroad. It is founded on Leibnitz’s philosophy that nothing happens without a cause or a reason.

“[…] all is for the best.” 

This phrase repeats frequently as Candide seeks to understand the meaning behind tragic events in his life and the lives of others. Voltaire uses the phrase in his satire to mock the optimistic philosophy that everything happens due to a divine (or cosmic) plan. When the idea is reduced to this simple phrase, it belies a blind acceptance for the way things are, no matter how unjust or preventable.

“First the cannon toppled about six thousand men on either side; then the muskets removed from the best of possible worlds between nine and ten thousand scoundrels who were infesting its surface. Next the bayonet proved sufficient reason for the death of a few thousand more. The total may well have amounted to thirty thousand or so corpses. Candide trembled like a philosopher, and concealed himself as best he could for the duration of this heroic butchery.” 

Voltaire describes the battle as seen through the eyes of Candide, who still perceives the world through the lens of Pangloss’ philosophy. The detached scientific language of cause-and-effect contrasts with the devastating (and terrifying) scene before Candide: thousands of human lives lost, which is rationalized by the optimistic belief that it is simply part of a cosmic order in which there could be no better outcome.