Optimism is an outlook on life such that one maintains a view of the world as a positive place. It is the philosophical opposite of pessimism. Optimists generally believe that people and events are inherently good, so that most situations work out in the end for the best.
A common conundrum illustrates optimism-versus-pessimism with the question, does one regard a given glass of water, filled to half its capacity, as half full or as half empty? Conventional wisdom expects optimists to reply, "Half full," and pessimists to respond, "Half empty" (assuming that "full" is considered good, and "empty", bad).
Another paradox sometimes associated with optimism is that the only thing an optimist cannot view as positive is a pessimist. Pessimism, however, as it acts as a check to recklessness, may even then be viewed in a positive light.
Philosophers often link the concept of optimism with the name of Gottfried Wilhelm Leibniz, who held that we live in the best of all possible worlds, or that God created a physical universe that applies the laws of physics, which Voltaire famously mocked in his satirical novel Candide. The philosophical pessimism of, for instance, Arthur Schopenhauer, provides an opposite pole to philosophical optimism.
The anarchist philosopher William Godwin demonstrated perhaps even more optimism than Leibniz. He hoped that society would eventually reach the state where calm reason would replace all violence and force, that mind could eventually make matter subservient to it, and that intelligence could discover the secret of immortality. Much of this philosophy is exemplified in the Houyhnhnms of Jonathan Swift's Gulliver's Travels.
The panglossian paradigm is a term coined by Stephen Jay Gould and Richard Lewontin to refer to the notion that everything has specifically adapted to suit specific purposes. Instead, they argue, accidents and exaptation (the use of old features for new purposes) play an important role in the process of evolution. Some other scientists however argue that the implication that many (or most) adaptionists are panglossians is a straw man.
Overoptimism, naive optimism or strong optimism, is the overarching mental state wherein people believe that things will more likely go well for them than go badly. Compare this with the valence effect of prediction, a tendency for people to overestimate the likelihood of good things happening rather than bad things.
Optimism bias is the demonstrated systematic tendency for people to be over-optimistic about the outcome of planned actions.
Personal optimism correlates strongly with self-esteem, with psychological well-being and with physical and mental health. Martin Seligman, in researching this area, criticises academics for focusing too much on causes for pessimism and not enough on optimism. He states that in the last three decades of the 20th century journals published 46,000 psychological papers on depression and only 400 on joy.
Optimism has been shown to be correlated with better immune systems in healthy people who have been subjected to stress.
Ideologically convinced optimists may defend failures in their hoped-for outcomes by discussing "misplaced optimism" rather than abandoning optimism altogether.
A number of scholars have suggested that, although optimism and pessimism might seem like opposites, in psychological terms they do not function in this way. Having more of one does not mean you have less of the other. The factors that reduce one do not necessarily increase the other. On many occasions in life we need both in equal supply. Antonio Gramsci famously called for "pessimism of the intellect, optimism of the will": the one the spur to action, the other the resilience to believe that such action will result in meaningful change even in the face of adversity.
Hope can become a force for social change when it combines optimism and pessimism in healthy proportions. John Braithwaite, an academic at the Australian National University, suggests that in modern society we undervalue hope because we wrongly think of it as a choice between hopefulness and naïveté as opposed to scepticism and realism.