“Doubt and mistrust are the mere panic of timid imagination, which the steadfast heart will conquer, and the large mind transcend.” Decades before the dawn of the positive psychology movement and a century before what neuroscience has taught us about the benefits of optimism, Helen Keller — the remarkable woman who grew up without sight and hearing until, with the help of her teacher Annie Sullivan, she learned to speak, read, write, and inhabit the life of the mind with such grace and fierceness that made her one of history’s most inspired intellectual heroes — penned a timeless treatise on optimism as a philosophy of life.