According to some of our classmates, only an important life merits an autobiography. According to Saint Augustine, only a life where one undergoes a profound experience is worth recording. Neither are completely right.
For our classmates to be entirely correct, on must assume that one wants the entire world to read your autobiography and possibly make money off of it. This may not always be the case. One could write an autobiography to for purely personal reasons. If I should ever have children, I would want to write a completely honest autobiography for them to read after my death, so that they can truly know their mother. Others write them just to keep track of their lives if they should forget small, yet significant details. They may not want the world to know their stories, but they want their stories recorded none the less.
Augustine is not entirely correct because his definition applies to every human being. We all experience the first time we disagreed with our parents, those who have been our moral compass since birth. We all take our first great risk, and wither bask in the glow of success or wallow in the shadows of defeat. We all experience our first love, and are all briefly devastated when we realize does not last forever. We all have experiences that have changed our views or altered our behavior. We may not instill our experiences with the profundity that Augustine has given his own, but that does not mean we do not have these experiences.
To put it briefly, a biography is what you make of it. If you want to change the world with your story, or just to make money off of it, you should at least fashion yourself with a sort of importance. If your motives are more modest, than this restriction does not apply.