To be optimistic, it is standardly assumed, is to have positive expectations. I here argue that this definition is correct but captures only one variety of optimism – here called factual optimism. It leaves out two other important varieties of optimism. The first – focal optimism – corresponds to the idea of seeing the glass half full. The second – axiological optimism – consists in the conviction that good is stronger than bad. Those three varieties of optimism are irreducible to each other and do not belong to a common kind, but exhibit essential connections I shall try to bring out.