Teachers have several different ways of looking at the concept of “theme.” Sometimes we ask students to state a theme as a “statement about human life or human nature,” rather than as just a single word or idea.
If we look at theme this way for “Casey at the Bat,” we have to consider what the crowd at the baseball game expects from Casey and what actually ends up happening. It is obvious from the poem’s description of Casey that he is considered to be a great hitter:
“If only Casey could but get a whack at that—
We’d put up even money now, with Casey at the bat.”
The fans at the game who haven’t left yet are watching, hoping that Casey will get a chance to hit. They clearly believe that he has a good chance to win the game for the home team. Keep in mind that in baseball, hitters fail more often than they succeed, even the great ones. So to be willing to put up “even money” on a hitters’ chances is to express great confidence in that hitter.
However, as is often the case in baseball, the best are likely to fail, and the poem ends this way:
But there is no joy in Mudville—Mighty Casey has struck out.
Themes should be universally true, so we cannot confine our theme to just baseball—we need to make it a little more general. A statement that encompasses the ideas presented in the poem in a universal way could be:
Even the best, despite the expectations of others, are liable to fail sometimes.
This is a viable theme (although not the only possible theme) because it makes a statement about human life that is universally true—it applies to all people, everywhere, all the time.