What was the basis for The Seven Commandments in Animal Farm?

The Commandments have their origin in the message Old Major, Mr Jones' prize boar and the most respected animal on the farm, had conveyed to the other animals during a secret meeting in the big barn. During the gathering he had informed the animals about a dream he had had and why it was so important.

In his message, Old Major mentioned, in part, the following:

No animal in England knows the meaning of happiness or leisure after he is a year old. No animal in England is free. The life of an animal is misery and slavery: that is the plain truth...

"But is this simply part of the order of nature? Is it because this land of ours is so poor that it cannot afford a decent life to those who dwell upon it? No, comrades, a thousand times no! ...

Why then do we continue in this miserable condition? Because nearly the whole of the produce of our labour is stolen from us by human beings. There, comrades, is the answer to all our problems. It is summed up in a single word--Man. Man is the only real enemy we have. Remove Man from the scene, and the root cause of hunger and overwork is abolished for ever.

"Man is the only creature that consumes without producing. He does not give milk, he does not lay eggs, he is too weak to pull the plough, he cannot run fast enough to catch rabbits. Yet he is lord of all the animals. He sets them to work, he gives back to them the bare minimum that will prevent them from starving, and the rest he keeps for himself. Our labour tills the soil, our dung fertilises it, and yet there is not one of us that owns more than his bare skin ..."

The old boar then urged the animals to fight against Man's tyranny and prepare for rebellion. He stated that he did not know when the revolution would happen but that when it did, the animals should be careful not to become like their vanquished masters. He, furthermore, stated:

"... And among us animals let there be perfect unity, perfect comradeship in the struggle. All men are enemies. All animals are comrades."

and

"... Whatever goes upon two legs is an enemy. Whatever goes upon four legs, or has wings, is a friend. And remember also that in fighting against Man, we must not come to resemble him. Even when you have conquered him, do not adopt his vices. No animal must ever live in a house, or sleep in a bed, or wear clothes, or drink alcohol, or smoke tobacco, or touch money, or engage in trade. All the habits of Man are evil. And, above all, no animal must ever tyrannise over his own kind. Weak or strong, clever or simple, we are all brothers. No animal must ever kill any other animal. All animals are equal."

Old Major completed his speech by then telling the animals about the dream he had had which related to the anthem, 'Beasts of England' that conveyed the utopian existence the animals would enjoy once Man had been removed.

The pigs then developed what Old Major had said into a system of thought which they called Animalism. From this, they fashioned the seven commandments which were written on the wall of the barn in big white letters by Snowball. The commandments would form the basis of their conduct on the farm and would be unalterable.

Ironically, exactly the opposite happened. The pigs, through a process of propaganda, manipulation, abuse and terror, managed to enslave the other animals and systematically convert the commandments to justify their greed and tyranny until only one amazingly fatuous rule was left:

All animals are equal, but some animals are more equal than others.