Why hadn't he realized this before? Everyone knew that if you divided reality by expectation, you got a happiness quotient. But when you inverted the equation-expectation divided by reality-you didn't get the opposite of happiness. What you got, Lewis realized, was hope. Pure logic: Assuming reality was constant, expectation had to be greater than reality to create optimism. On the other hand, a pessimist was someone with expectations lower than reality, a fraction of diminishing returns. The human condition meant that this number approached zero without reaching it-you never really completely gave up hope; it might come flooding back at any provocation.