Panglossianism

Panglossianism is baseless optimism of the type possessed by the character Dr. Pangloss in Voltaire's novel Candide. Pangloss believed that "we live in the best of all possible worlds". The real-world model for Dr. Pangloss was the philosopher Gottfried Leibniz.

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The phrase Panglossian pessimism has been used to describe the pessimistic position that, since this is the best of all possible worlds, it is impossible for anything to get any better.