1. (n.) One who holds the opinion that all events are ordered for the best.

2. (n.) One who looks on the bright side of things, or takes hopeful views; -- opposed to pessimist.

Leibnizian optimist Pollyanna aspirant aspirer chiliast dreamer hopeful hoper idealist irrepressible optimist millenarian millennialist millennian perfectibilist perfectibilitarian perfectionist philosophical optimist positivist ray of sunshine utopian