One prominent theme is abuse of power, or, to put it another way, the corrupting influence of political power. The animals' revolution begins with the best of intentions, as expressed by Old Major in his speech. They wanted to achieve a better life and an authentic equality, free of the injustices characterized their lives under the humans. But no sooner is Animal Farm established than the pigs, who emerged as leaders of the rebellion, began to use their power to subvert the very principles of the revolution to make their lives better. At first, the corruption is subtle, beginning with the missing milk and apples. By the end of the book, though, the pigs have become so corrupted that the other animals cannoth distinguish them from the humans.
Another important theme is the control, or manipulation of, information. This is, in fact, one of the ways in which the pigs are able to consolidate their power. Squealer's speeches are full of glaring falsehoods, but the animals accept them even when they know better. His rewriting of Snowball's role in the Battle of the Cowshed is a particularly glaring example. But this theme is best reflected in the Seven Commandments, which change throughout the book to suit Napoleon's needs, with a minimum of incredulity from the other animals. Orwell's point is to demonstrate how thoroughly effective propagandists can manipulate the minds of people, determining the very nature of truth itself.
In general, I think the major themes of the book are these:
- It talks about how revolutions can turn into totalitarian governments.
- It talks about how leaders can take power away from the people by lies and propaganda.
- It talks about how people can let these things happen.
To me, this relates to the past in that it explains how the people of the Soviet Union were able to allow their country to get to be the way it was. It could apply to Nazi Germany as well.
As for the present and the future, I would say that the theme of the government lying to the people could be important. I am not saying that the government lies to us the way Napoleon and Squealer do in the book, but governments (as well as anyone in the public eye, like oil companies and car companies and banks) do try to spin the truth and that is something we must all look out for.