At the beginning of chapter II, the author states that "Snowball was a more vivacious character than Napoleon, quicker in speech and more inventive," and many of the early slogans can be attributed to him. For example, it is Snowball that paints and reads out the seven commandments that become the basis for most of the slogans.
The seven commandments are as follows:
1. Whatever goes upon two legs is an enemy.
2. Whatever goes upon four legs, or has wings, is a friend.
3. No animal shall wear clothes.
4. No animal shall sleep in a bed.
5. No animal shall drink alcohol.
6. No animal shall kill any other animal.
7. All animals are equal.
When the animals struggle to learn the commandments by heart, Snowball condenses them into the much easier to remember "Four legs good. Two legs bad."
In the end, Napoleon, who doesn't seem have the same intelligence as Snowball and therefore the ability to control the animals through rhetoric alone, chases Snowball off the farm and starts to lead in a more brutal manner.
In the final chapters, Napoleon's ideas seem nothing more than a twist on Snowball's ideas and he slowly changes the seven commandments to fit his own lifestyle. For example, after Napoleon and the other pigs get drunk, Napoleon changes "No animal shall drink alcohol" to "No animals shall drink alcohol to excess." After Napoleon kills animals who he says are traitors, he changes "No animal shall kill any other animal" to "No animal shall kill any other animal without cause."
By the end of the book, the seven commandments have been reduced to one line. "All animals are equal, but some are more equal than others."