If Animal Farm is not an entirely sad story, I shudder to think of what could be one. I think that Orwell set out to construct a portrait whereby individuals learn about the dangers of not being politically active. Part of the sadness in Orwell's story is that it speaks to what happens when individuals relinquish political activity to those who abuse the public trust. The other animals did not actively learn to read or work towards understanding Old Major's vision of Animalism. The pigs recognized the potency of it and through this, ascend into power. The other animals "trust" the pigs, and this becomes the basic element of sadness in the story. By the end of it, there is little in way of redemption in the story. The pigs have won, establishing themselves and their superiority for some time, effectively silenced all voices of dissent, and have ensured that the structure that keeps them at the top of the political pyramid and all others underneath is embedded in life on the farm. The hopes and aspirations of political change have been supplanted by the expediency of political power. This is a fairly sad and rather bleak view of political reality, but one that Orwell feels absolute in terms of what is stressed and what he believes. It is for this reason I would argue that the story is an entirely sad one.