I recently read this article by Bradley P. Beaulieu, discussing ways in which characters change and grow and whether or not this is necessary to a good story. This had me thinking not only about the ways in which characters might change, but the reasons for them—what inspires characters to change, either consciously or unconsciously, and which of these are most effective for a story?

The thing is, people don’t like to change—we’re a rather sedentary species. The saying “if it ain’t broke, don’t fix it” is an attitude for more than just appliances, and inertia affects more than just objects:

“An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.” —Newton’s First Law of Motion (aka the Law of Inertia)

So what sort of “unbalanced force” can make a character change?