Vague optimism can be defined as viewing the future in an optimistic, positive, hopeful light but having no concrete reason for doing so. A person who feels vague optimism senses that improvements are on the horizon yet only has a vague idea of what those improvements could possibly be or even no idea at all. The person has even a vaguer sense of how the improvements will arise since the situation currently looks so bleak.
At the time that Franklin D. Roosevelt took the presidency during the Great Depression, Roosevelt knew he needed to instill within his citizens vague optimism in order to begin to overcome the Great Depression. Therefore, in his very first inaugural address to the nation, Roosevelt told the American people that he firmly believes "the only thing we have to fear is fear itself--nameless, unreasoning, unjustified terror which paralyzes needed efforts to convert retreat into advance" (History Matters, George Mason University). In other words, according to Roosevelt, fear of the bleak future immobilizes us; vague optimism in the possible future empowers us. Narrator Scout makes a reference to Roosevelt's inaugural address in the opening chapter of Harper Lee's To Kill a Mockingbird when she notes the following:
But it was a time of vague optimism for some of the people: Maycomb County had recently been told that it had nothing to fear but fear itself. (Ch. 1)
Harper Lee ties this "vague optimism" in to her greater themes throughout the book such as her theme concerning overcoming injustices due to racial discrimination. The best moment in the book in which we see "vague optimism" being connected with Lee's greater theme of injustice is when Miss Maudie says the following to Scout, Jem, and Dill the day after Tom Robinson's trial:
[A]s I waited [for the Finches to return home from the trial] I thought, Atticus Finch won't win, he can't win, but he's the only man in these parts who can keep a jury out so long in a case like that. And I thought to myself, well, we're making a step--it's just a baby step, but it's a step. (Ch. 22)
In other words, Miss Maudie is explaining that Atticus's actions concerning his devoted defense of Robinson has impacted society. It is not yet a significant impact; there is still much to be done to overcome social injustices, but society, through Atticus and others like him, has made a tiny "baby-step" towards a more just society. That tiny baby step is enough to give members of society who want it, like Miss Maudie and the Finch children, vague optimism about the creation of a more just society in the future just as Roosevelt gave the American people vague optimism about overcoming the Great Depression.