Emmanuel Goldstein is introduced as the Enemy of the People during the Two Minutes Hate at the beginning of the novel. He was once an important member of the Party but became a traitor. Although he was sentenced to death, he escaped and formed the Brotherhood, an organized body of rebels committed to the destruction of the Party and the party’s way of life.
Like Big Brother, Goldstein very likely does not exist as an actual person, but rather, is a propaganda tool used by the Party to stir up emotion in the citizens. Goldstein functions as a threatening but ill-defined monster that the Party uses to keep citizens in line and prevent rebellion. Like Eastasia and Eurasia, Goldstein provides the Party with an enemy to act against. When the Party does things that hurt the populace, their actions can be blamed either on terrorist attacks by Goldstein’s followers or on necessary precautions to prevent further attacks.
Goldstein’s most significant contribution to the plot of the novel is as alleged author of the book The Theory and Practice of Oligarchical Collectivism. The book contains the truth of the Party as well as a model for how to overthrow them, as is quoted at length in Book Two: Chapter IX of 1984. These sections go into detail about how the Party uses endless war, the manipulation of history, and the threat of the Thought Police to control the population. The book also lays out a hopeful plan of rebellion whereby the tiny resistances made by disobedient Party members eventually accumulate to become powerful enough to tear down the Party.
Winston gets a copy of Goldstein’s book from O’Brien and is hugely affected by what he reads in this book. Although the content of the book seems to be largely accurate to the way the Party really works, we later learn that the book was not written by Goldstein, but by O’Brien and a committee of Party loyalists as another prop and trap for drawing in thought-criminals.