Pessimism is the tendency to focus on and emphasise the negative aspects of life. The word pessimism comes from the Latin pessimus meaning ‘the worst.’
Critics of Buddhism sometimes accuse it of being pessimistic, although significantly there is no Pali equivalent for either the words pessimism or pessimist. The opposite of pessimism might be called positivism, the tendency to focus only on the attractive, the liked and the positive. Buddhism sees both these attitudes as lacking balance and likely to end in either confusion or despair. To ignore or deny the negative (sickness, old age, death, evil, etc) is to be completely unprepared for them when finally confronted by them. To fail to see or appreciate the positive (beauty, goodness, virtue, happiness, joy etc) is to become gloomy, withdrawn and bitter. Both attitudes are unlikely to help one progress in Dhamma. The Buddha taught that we should try to develop ‘a knowledge and vision of things as they are.’
Buddhism is sometimes confused as a pessimistic religion since it refers to the suffering in life. But this view fails to look at the entirety of The Four Noble Truths. It is not that all life is suffering, but rather that all unenlightened life is suffering. There can be suffering, but there is also a way out of the suffering and that is why there are four noble truths, not one.