I do not see what right one animal has to deprive another of its small importance, to prevent himself from losing more: if this theory be generally admitted, a young man might kill an old man, to save his own longer expectant life. And are we authorized to kill one animal for the benefit of another of its species? If they should overstock the world, it will then be time to begin to destroy them. It seems however more just that nature should take her course, and that man should be neutral till provoked. It is certainly easier for him to destroy others than to suffer inconvenience himself; but that does not make it right. We have not however at present any reason to complain of the too great fecundity of those animals we use for food, etc., and we even take great pains to produce them, not for their own enjoyment, but for the good and pleasure we derive by destroying and tormenting them.

Y: As you think it wrong for man to kill other animals for food, do you also think it wrong that animals should devour each other? As this is the general law of nature.
Z: It appears wrong, according to the rules by which we govern our own actions to each other; and should I witness the attempt in any animal of destroying another, I would endeavour to frustrate it; though this might probably be wrong.

Yet we are not always justified in concluding that the killing of animals causes a less number to exist; because some of them are carnivorous, and by being killed they can no longer kill others: while others are graminivorous, and when they can no longer eat up the fruits of the soil, other animals may live upon such fruits instead; still there is no justification of slaughter, as the identical lives are certainly thereby destroyed; and if such an excuse be admitted, it must apply by the same rule to the slaughter even of human beings. But however this may be, it is evident that by far the greatest number of animals live in terror and die by violence from their devourers, and the males also by the attacks of each other, besides pestilence, diseases, accidents and starvation, few living their natural time; while by means of many being sacrificed, a few are enabled to live like in a ship of short provision, though without an equitable casting of lots, but by the law of force over weakness; and this law not being confined to dumb animals, but ruling the lots of man as well as of animals, though its operations on human life may be more concealed, but here also population is kept in check by want of food and by warfare; among mankind itself justice is little more than a name, might being the chief law observed: here, too, the strong destroy and oppress the weak; some are enabled to live and multiply, while many starve and live in celibacy to prevent an overflow, which, notwithstanding, does arise: dispute and warfare then result in which some are destroyed and some preserved. But no person, however virtuous, can live in comfort without consuming more than his share. Such is the world we live in, however Pope may contend that "virtue alone is happiness below."

Much has also been said about the cruelties inflicted by animals upon one another. But I must emphasize that, in their original wild state, and with rare exceptions, animals kill only for food, not for the sake of killing. That is a prerogative peculiar to humankind.

People kill nonhuman animals for food, for their skins, and sometimes just for fun. We enslave animals and force them to work for us. We experiment on them and justify their suffering in terms of our advantage. Because most of us want to be able to view ourselves as good people (and, perhaps more importantly, because we want others to view us as good people), we may be motivated to view nonhumans in such a way that these activities are rendered morally unproblematic. One way to do this is to view other animals as utterly different from us.

But as the multiplication of animals exceeds the vegetable food, it is true that by killing some of the animals not any the less live, as they are only killed instead of starved. This, we are sorry to confess, is the system of nature, but this is no justification of a partial destruction of lives. It is generally, tritely enough said, that animals most be destroyed by every means they now are,—that destruction is the general law of nature, and otherwise overstock would result; let us for a moment admit it, we must then on the same plea massacre human beings, namely, to prevent overstock; and we ask the advocates of this principle just to point out what crime consists of, as it seems to us that most crimes can be defended on the same ground.

The destruction of life is always a crime. There may be certain cases in which it is the lesser of two evils; but here it is needless and without a shadow of justification, for it happens only because of the selfish unscrupulous greed of those who coin money out of the agonies of the animal kingdom in order to pander to the perverted tastes of those who are sufficiently depraved to desire such loathsome aliment. Remember that it is not only those who do the obscene work, but those who by feeding upon this dead flesh encourage them and make their crime remunerative, who are guilty...of this awful thing. Every person who partakes of this unclean food has his share in the indescribable guilt and suffering by which it has been obtained.

It is often said, as an excuse for the slaughter of animals, that it is better for them to live and to be butchered than not to live at all. … In fact, if we once admit that it is an advantage to an animal to be brought into the world, there is hardly any treatment that cannot be justified by the supposed terms of such a contract. Also, the argument must apply to mankind. It has, in fact, been the plea of the slave-breeder; and it is logically just as good an excuse for slave-holding as for flesh-eating. It would justify parents in almost any treatment of their children, who owe them, for the great boon of life, a debt of gratitude which no subsequent services can repay. We could hardly deny the same merit to cannibals, if they were to breed their human victims for the table, as the early Peruvians are said to have done.

Getting rid of predation isn't a matter of moralising. A python who kills a small human child isn't morally blameworthy. Nor is a lion who hunts and kills a terrified zebra. In both cases, the victim suffers horribly. But the predator lacks the empathetic and mind-reading skills needed to understand the implications of what s/he is doing. Some humans still display a similar deficit. From the perspective of the victim, the moral status or (lack of) guilty intent of a human or nonhuman predator is irrelevant. Either way, to stand by and watch the snake asphyxiate a child would be almost as morally abhorrent as to kill the child yourself. So why turn this principle on its head with beings of comparable sentience to human infants and toddlers? With power comes complicity.

Opposers of compassion urge: ‘If we should live on vegetable food, what shall we do with our cattle? What would become of them? They would grow so numerous they would be prejudicial to us—they would eat us up if we did not kill and eat them.’ But there is abundance of animals in the world whom men do not kill and eat; and yet we hear not of their injuring mankind, and sufficient room is found for their abode. Horses are not usually killed to be eaten, and yet we have not heard of any country overstocked with them. … Cattle are at present an article of trade, and their numbers are industriously promoted. … Self-preservation justifies a man in putting noxious animals to death, yet cannot warrant the least act of cruelty to any being. … Some animals are savage and unfeeling; but let not their ferocity and brutality be the standard pattern of the conduct of man. Because some of them have no compassion, feeling, or reason, are we to possess no compassion, feeling, or reason?

To a man whose mind is free there is something even more intolerable in the sufferings of animals than in the sufferings of man. 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.

The scientist who considers himself absolutely "objective" and believes that he can free himself from the compulsion of the "merely" subjective should try — only in imagination of course — to kill in succession a lettuce, a fly, a frog, a guineapig, a cat, a dog, and finally a chimpanzee. He will then be aware how increasingly difficult murder becomes as the victim's level of organisation rises. The degree of inhibition against killing each one of these beings is a very precise measure for the considerably different values that we cannot help attributing to lower and higher forms of life. To any man who finds it equally easy to chop up a live dog and a live lettuce I would recommend suicide at his earliest convenience!

Y: I suppose you also deem it a crime to drink, as you destroy myriads of animals in the water of every draught?
Z: I consider this an evil, but not a crime, because I do not cause or wish them to be there, and would assist them to escape if possible. They have no more claim to the water than I have; and we know so little of the nature of these animals, that we are not even sure that they die when the water is drunk; the very fact of their being there is concealed from us, and but for the microscope we should never have known it. I however consider it wrong to waste water in anyway which may injure the animalcula.

Animals more obviously violate the concept of goodness, for none can live without tearing and devouring other organized beings, whether vegetables or other animals, or else sapping their strength as noxious parasites. The larger ambulatory animals can hardly move without crushing the herbage and multitudes of small creeping things; and all compete with each other for space and nourishment in the same manner as plants, but often far more violently. Moreover, they struggle for mates in a fashion wholly unknown among vegetables, even the milder herbivores sometimes exhibiting in their quarrels with rivals a fury that astounds us. Thus none is wholly good; yet those which devour only vegetation seem to be endowed by nature with a capacity for goodness lacking in those which kill and tear for food creatures more akin to themselves; while the fiercest kinds, which destroy living things that they do not require to sustain their own lives, fall most conspicuously short of goodness.