op·ti·mism 
(ŏptə-mĭz′əm)
(ŏptə-mĭz′əm)n.
1. A tendency to expect the best possible outcome or dwell on the most hopeful aspects of a situation.
2. Philosophy
a. The doctrine, asserted by Leibniz, that this world is the best of all possible worlds.
b. The belief that the universe is improving and that good will ultimately triumph over evil.
[French optimisme, from New Latin optimum, the greatest good; see OPTIMUM.]