Orwell starts off the work with the basic premise that at the heart of all political change lies the ability to dream. It is Old Major's "dream" that causes all the animals to meet up in the shed. It is this "dream" that he articulates which becomes the basis for political reality. The pigs become caretaker of this dream. The revolution is the political embodiment of this dream and with the animals' success, the dream of change is realized.
From this point, Orwell illuminates how the desire to control political reality might chip away at such dreams. Snowball embraces the hope of converging political reality and political dreaming, but the forces of Squealer and Napoleon are much more driven by political reality. Snowball's expulsion is a distinct moment in which political reality is shown to be much more important and essential than political dreams. As Napoleon increases his control on the farm, this element becomes more pronounced. By the end, when there is no physical difference between animals and humans, it has become clear that political reality in the hands of those in the position of power is much more preferable to political dreaming.