In his speech to the animals in the big barn, Old Major expounds certain principles which the animals are to live by if their rebellion should succeed. Most of these propositions have to do with the animals treating one another as equals and not adopting human characteristics or behavior. Old Major feels that everything about humanity is evil and that the animals, once they have gained their freedom, should never become like their abusive, exploitative, and tyrannical masters.
After Old Major's death, Squealer, Snowball, and Napoleon, the three leading pigs on the farm, develop Old Major's teachings into a complete system of thought that they call Animalism. After the Rebellion, the animals are in complete control of the farm. The pigs, through their studies over a period of three months, reduce the principles of Animalism to Seven Commandments. These laws will be the foundation on which the animals' lives are based and are unalterable. Snowball then inscribes the list of rules on the barn wall where they can be clearly seen.
The information above makes it clear that the Seven Commandments are the result of a joint effort by all the pigs. The formulation of the Commandments is the result of the pigs' investigation and study of all the concepts contained in the theory of Animalism and is an expression of its practical application.
It is ironic, however, that the very same animals who develop the Commandments are the first ones to alter them to suit their wants and their greed in spite of the fact that they have said that the rules must be unalterable and permanent. In fact, by the end of the novel, all the commandments have been replaced by a single, paradoxical instruction that:
All animals are equal, but some animals are more equal than others.
This equivocal statement becomes a symbolic testament to the unequal equality that the majority of the animals on the farm are exposed to, and it is a damning indictment of the pigs' manipulation and greed. Old Major would have been ashamed.