"Memory produces hope in the same way that amnesia produces despair," the theologian Walter Brueggeman noted. It's an extraordinary statement, one that reminds us that though hope is about the future, grounds for hope lie in the records and recollections of the past. We can tell of a past that was nothing but defeats and cruelties and injustices, or of a past that was some lovely golden age now irretrievably lost, or we can tell a more complicated and accurate story, one that has room for the best and worst, for atrocities and liberations, for grief and jubilation. A memory commensurate to the complexity of the past and the whole cast of participants, a memory that includes our power, produces that forward-directed energy called hope. 

Amnesia leads to despair in many ways. The status quo would like you to believe it is immutable, inevitable, and invulnerable, and lack of memory of a dynamically changing world reinforces this view. In order words, when you don't know how much things have changed, you don't see that they are changing or that they can change. Those who think that way don't remember raids on gay bars when being queer was illegal or rivers that caught fire when unregulated pollution peaked in the 1960s or that there were, worldwide, 70 percent more seabirds a few decades ago and, before the economic shifts of the Reagan Revolution, very, very few homeless people in the United States. Thus, they don't recognize the forces of change at work. 

One of the essential aspects of depression is the sense that you will always be mired in this misery, that nothing can or will change. It's what makes suicide so seductive as the only visible exit from prison of the present. There's a public equivalent to a private depression, a sense that the nation or the society rather than the individual is stuck. Things don't always change for the better, but they change, and we can play a role in that change if we act. Which is where hope comes in, and memory, the collective memory we call history." 

— Rebecca Solnit, Hope in the Dark: Untold Histories, Wild Possibilities