What does it mean for an Essay to be over-determined?

I'm currently reading an Essay by George Orwell - Shooting an Elephant (1936). Where Orwell tells a story of how he, an an Indian Imperial Police Officer, killed an elephant infront of a crow of people daring him to prove himself. In the biography before the essay, it states that many "contemporary historians, agree that the shooting and Orwell's essay were both "Over-Determined"