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.
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.