Class Warfare
One of the main tenets of Animalism is that all animals are equal. But quite quickly the pigs begin to refer to themselves as "mindworkers" to distinguish themselves from the other animals, who are physical laborers. Over time, this sense of separation takes hold: the pigs begin to discourage their children from playing with the children of the other animals, and then establish themselves as absolute rulers of the "lesser" menial laborers. Animal Farm shows how differences in education and occupation lead to the development of class, which leads inevitably to class warfare, in which one class seeks to dominate the other. Animal Farm suggests that the "mindworking" class will almost always prevail in this struggle.
Animal Farm doesn't just focus on the upper classes, however. In fact, it focuses more closely on the oppressed working class. The farm animals work so hard that they have no time to learn or educate themselves or think deeply about their world. Instead, they're taught that work is their contribution to society, their way to freedom. Boxer believes that "I will work harder" is the answer to every problem, though he never perceives that the pigs exploit his effort. Benjamin occupies the other extreme: he recognizes what's going on, but his cynicism stops him from taking action against the pigs. In the end, Animal Farm implies that whether because of ignorance, inaction, or fear, the working class allows itself to be dominated by the "mindworkers."