In George Orwell's Animal Farm, how are the pigs able to deceive the other farm animals under the guise of "animalism"? What lies do Napoleon and...

The pigs, the most intelligent of the animals, change the tenets of animalism to serve their own interests. For example, though the animals all agree that they won't ever live in a house or use a bed, the pigs insist that they "absolutely" must have the quiet of the farmhouse to think and plan, and when they use human beds, they initially justify it because they are not using sheets. They always have a handy rationalization for breaking or bending the rules.  

Napoleon says that the farm must engage in trade, though the animals had previously resolved never to trade. He justifies it as not for any "commercial purpose," but simply to obtain materials that the animals urgently need for building the windmill. When some of the animals suggest that this violates animalism, the dogs growl at them in an intimidating way and the sheep begin their mindless bleating of "four legs good, two legs bad." Here we see that fear and group thinking drown out dissent. The pigs will repeatedly use fear, especially fear of the dogs, and the sheep's propensity to mindless chanting, to exert control. Later, Squealer will insist that the animals had never agreed not to engage in trade or use money. He says that idea was probably a lie started by Snowball, who has been labelled the enemy of Animal Farm.

Most of the animals have integrity, believe in the tenets of Animalism, and want the farm to succeed. They want to believe their leaders have their best interests at heart. They are basically honest themselves, so it is hard for them to believe the pigs would lie so blatantly or put their own interests ahead of animalism. The pigs are craftier than the other animals, so they become skilled at twisting and shading the truth. They don't overturn the tenets of animalism all at once or adopt their privileges all at once. They move gradually, step by step, all the while doing everything they can to confuse the animals. Orwell is showing how humans can equally be deceived: the story is a warning against being too trusting and gullible.