For of all creatures that breathe and creep about on the earth, there is none so miserable as man.

man is the only animal which causes pain to others with no other object than causing pain…No animal ever torments another for the sake of tormenting: but man does so, and it is this which constitutes the diabolical nature which is far worse than the merely bestial

Humans — who enslave, castrate, experiment on, and fillet other animals — have had an understandable penchant for pretending animals do not feel pain. A sharp distinction between humans and 'animals' is essential if we are to bend them to our will, make them work for us, wear them, eat them — without any disquieting tinges of guilt or regret. It is unseemly of us, who often behave so unfeelingly toward other animals, to contend that only humans can suffer. The behavior of other animals renders such pretensions specious. They are just too much like us.

We identify with the powerless and the vulnerable—the victims, all those dominated, oppressed, and exploited. And it is the nonhuman animals whose suffering is the most intense, widespread, expanding, systematic, and socially sanctioned of all. What can be done? What are the patterns underlying effective social struggles?

Arguments to the effect that it is wrong to cause pain and suffering to animals are often rejected by claiming that animals simply do not suffer. … Ironically, it is precisely upon the assumption that animals do suffer from stress, fear, and pain in a manner similar to humans that the validity of much of animal experimentation rests. Few, if any, conditions are studied as widely in animals as are pain, stress, ulcers, fear, and anxiety.

As far as fidelity is concerned, there is no animal in the world as treacherous as man.

The suggestion that we should take wild animal suffering seriously as an ethical issue runs contrary to many of our most powerful biases. It concerns animals for which we, instinctively, feel very little sympathy, and whose suffering we humans did not cause and thus do not feel obliged to help alleviate. The suffering is also far removed from our daily lives and it exists on a scale of magnitude so large that it is hard for us to grasp it. Finally, wild animal suffering challenges a romantic view of nature, which is deeply held by many, and since all large-scale solutions lie far in the future, it is easy for us simply to disregard it.

No pain can be greater than the pain of one person. [...] In other words, no suffering can be greater than that of one human being. [...} The whole planet cannot suffer more than a lone soul.

There is nothing alive more agonized than man / of all that breathe and crawl across the earth.

He could not think of the animals without shuddering in anguish. He looked into the eyes of the beasts and saw there a soul like his own, a soul which could not speak; but the eyes cried for it: "What have I done to you? Why do you hurt me?" He could not bear to see the most ordinary sights that he had seen hundreds of times—a calf crying in a wicker pen, with its big, protruding eyes, with their bluish whites and pink lids, and white lashes, its curly white tufts on its forehead, its purple snout, its knock-kneed legs:—a lamb being carried by a peasant with its four legs tied together, hanging head down, trying to hold its head up, moaning like a child, bleating and lolling its gray tongue:—fowls huddled together in a basket:—the distant squeals of a pig being bled to death:—a fish being cleaned on the kitchen-table.... The nameless tortures which men inflict on such innocent creatures made his heart ache. Grant animals a ray of reason, imagine what a frightful nightmare the world is to them: a dream of cold-blooded men, blind and deaf, cutting their throats, slitting them open, gutting them, cutting them into pieces, cooking them alive, sometimes laughing at them and their contortions as they writhe in agony. Is there anything more atrocious among the cannibals of Africa? To a man whose mind is free there is something even more intolerable in the sufferings of animals than in the sufferings of men. For with the latter it is at least admitted that suffering is evil and that the man who causes it is a criminal. But thousands of animals are uselessly butchered every day without a shadow of remorse. If any man were to refer to it, he would be thought ridiculous.—And that is the unpardonable crime. That alone is the justification of all that men may suffer.

I have observed cats and dogs, horses, cattle and sheep under every kind of pain, and I do unhesitatingly say that they suffer as we suffer.

Much as animals suffer in a natural state, much more do they seem to suffer when under the dominion of the generality of men. What suffering in the former can be supposed to equal the constant torture of a hackney-coach horse?

But [the human treatment of nonhuman animals is] nothing compared to the suffering doled out by Nature. It boggles the mind to consider the billions upon billions of animals stalked and killed or eaten alive by predators or who died slowly and painfully, decimated by disease, famine, or drought.
So it is that we must face a sobering fact: the history of our planet is a history stuffed with undeserved, horrific evil and suffering.

The most striking quality that humans and animals have in common is the capacity to experience suffering. Why do we still blind ourselves, now at the beginning of the twenty-first century, to the immeasurable suffering that we inflict on animals, knowing that a great part of the pain that we cause them is neither necessary nor unavoidable? Certainly we should know that there is no moral justification for inflicting needless pain and death on any being.