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Peter Singer and the Prevention of Cruelty to Animals (2004)


The great ethical change in Europe in the 19th century towards the treatment of animals were chiefly due to one man – Jeremy Bentham. Before the 19th century maltreatment of animals was not generally  subject to adverse moral judgement largely because the Church held that animals, unlike human beings, lacked independent moral significance. Bentham insisted that they did. The criterion he relied upon to justify that position is that both humans and animals experienced pleasure and pain.

Peter Singer elaborated upon this and maintained that the principle of equality applied to them both. By this he did not mean that in any given situation humans and animals should receive identical treatment but that both had had an equal claim to have their interests consulted. Because of the inherent limitations of animals, their interests would be qualified and thus less than human beings. The essay explains this proposition and criticises it. It agrees that animals do possess independent moral significance but inferior to that of human beings. The essay explores these differences in the moral significance of each and how that should affect our treatment of animals.


Before the nineteenth century cruelty to animals was quite generally indulged in for popular amusement.  Henry VIII was himself very fond of cock-fighting, as was James I.  James appointed a special cock master to breed and train his cocks.  Sometimes brandy was given just before a fight to provoke their spirit.  In 1607 a Norfolk vicar wrote a commendation of the sport.  Puritans protested but they did not do so on the ground of cruelty but because cock fights were held on a Sunday.  Cock fighting continued until well into the nineteenth century, often in conjunction with horse racing.  As late as June 1, 1822, the Times advertised, ‘A main of cocks will be fought on Monday 3 June at the Cockpit Royal Tyburn Street Westminster between the gentlemen of Middlesex and Shropshire for five guineas a battle and fifty guineas for the best battler’

A variant of cock-fighting was the throwing of cocks in which the cock was partly buried in the ground or fastened to a stake and stoned to death. 

In the seventeenth century a special amphitheatre was built at Paris Gardens, Southwark, for bull and bear-baiting.  Seating was provided for 1,000 spectators.  Later, a second ring was built exclusively for bear-baiting.  In villages, a bear would be chained to a stake on the village green and there set upon by dogs of all kinds. 

Maltreatment of animals was due partly to cruelty and partly to indifference.  Nevertheless, it was encouraged, or at least not discouraged by European thought. Other civilisations have had a positive attitude towards the treatment of animals  The Chinese, for example, from an early stage enjoined kindness to animals.  Kan-Yung-P’ien (the book of Deeds and Rewards), a popular work of the Sung Dynasty (960-1227), goes furthest in its demands for compassion towards animals: ‘Have a pitiful heart for all creatures.  If one sees animals in need one must take heed to keep them and preserve their lives.’

The stoics however taught that the universe exists only for rational beings and they thus excluded any relationship between humans and animals.*

Jesus appears as equivocal in the New Testament.  In Luke he is reported as saying, ‘are not five sparrows sold for two farthings, and not one of them is forgotten before God?’ and he adds ‘ye are of more value than many sparrows’.  Nevertheless he recognised that the birds belonged to and were not forgotten by God.

Apart from scriptural literalism, it may have been thought that the New Testament ethic of compassion would embrace animals, but Paul absorbed stoic philosophy on the relationship between humans and animals and drew a clear distinction between God’s concern for man and for other animals.  Paul also relied upon scriptural authority citing Deuteronomy, and asked rhetorically, ‘Doth God take care of the oxen?’. 

The Pauline-stoic position was reinforced by the authority of St. Augustine in the fifth century:

“Christ himself shows that to refrain from the killing of animals and the destroying of plants is the height of superstition for, judging that there are no common rights between us and the beasts and trees, who sent devils into a herd of swine and with a curse withered the tree on which he found no fruit”.

St. Augustine pointed out that ‘the swine had not sinned nor had the tree’. 

This became a standard Christian teaching.  Aquinas taught that a callousness towards animals was wrong not because it was wrong in itself but because it might lead to indifference to human suffering. 

There was an additional argument advanced by the stoics and supported by Aquinas.  It was that the killing of animals and their related suffering was justifiable in so far as it was necessary to preserve human beings.  This argument based upon a hierarchy of importance in living things is conceptually distinct from the proposition that animals lacked an immortal and divine soul by virtue of which they were excluded from God’s realm. 

The Church held that man could do more or less what he liked with animals. St. Francis whose love of animals was displayed throughout his life had no influence on Christian philosophy.  The Catholic tradition was enunciated by Leo XIII in Rerum Novarum:

“But animal nature, however perfect, is far from representing the human being in its completeness, and it is in truth humanity’s humble hand maid, to serve and obey.  It is the mind or reason, which is the predominant element in us who are human creatures; it is this which renders a human being human and distinguishes him essentially and generally from the brute”.

As late as the middle of the nineteenth century Pope Pius IX refused to allow a Society for the Prevention of Cruelty to be established in Rome, on the ground that to do so would imply that human beings have duties towards animals.

Whatever their other differences the Church and John Locke were agreed that, in Locke’s words a ‘person’ was a ‘thinking, intelligent being that has reason and reflection’.  Descartes (1596-1650), the most influential philosopher of the Age, drew the most extreme conclusions from the ‘soul-less’ character of animals.  Descartes held all matter to be governed by mechanistic principles.  The human body was matter and therefore machine-like.  But human beings had a soul (which Descartes equated with consciousness). This was not governed by mechanistic principles.  Only human beings possessed a soul and therefore non-human animals were pure matter.  Non-human animals were thus governed solely by mechanistic principles.  Accordingly, when animals appeared to be suffering, this was not really so.  They were emitting sounds as if in response to a lever.  For to allow them feelings would mean that they were conscious and therefore had a soul, which was contrary to scripture.  Descartes thus accepted without qualification experimentation on animals.

As to this, Voltaire, giving expression to Enlightenment humanism, wrote that ‘there are barbarians who seize this dog, who so greatly surpasses man in fidelity and friendship, and nail him down to a table and dissect him alive, to show you the mesariaic veins!  You discover in him all the same organs of feeling as yourself.  Answer me mechanist, has nature arranged all the springs of feeling in this animal to the end that he might not feel?’*

The first writer in Europe since Roman times to condemn cruelty to animals as a wrong in itself was the French essayist, Montaigne (1533-1592).  In his essay on ‘Cruelty’, he wrote that ‘we have a general duty to be humane’ to animals and that it is a presumption that man ‘withdraws and separates himself from the crowd of other creatures’.

In the eighteenth century David Hume argued that human intelligence and animal intelligence functioned in the same way.  He said that ‘we should be bound by the laws of humanity to give gentle usage to those creatures’.  Neither Hume nor Montaigne suggested it was sufficient for humans to act merely justly towards animals.  It is not, Hume said, ‘the cautious, jealous virtue of justice’ but humanity.  Hume led to Bentham.  More than anything else it was Bentham’s philosophy and active persistence that resulted in the changed attitude towards animals.

In his ‘Introduction to the Principles of Morals and Legislation’, Bentham wrote:

“The day may come when the rest of the animal creation may acquire those rights which never could have been withdrawn from them but by the hand of tyranny.  The French have already discovered that the blackness of the skin is no reason why a human being should be abandoned without redress to the caprice of a tormentor.  It may one day come to be recognised that the number of legs, the vellosity of the skin, the termination of the os sacrum, are reasons equally insufficient for abandoning a sensitive being to the same fate.  What else is it that should trace the insuperable line?  Is it the faculty of reason, or perhaps the faculty of discourse?  But a full-grown horse or dog is beyond comparison a more rational, as well as a more conversable animal than an infant of a day, a week or even a month, old.  But suppose they were otherwise, what would it avail?  The question is not, can they reason?  Nor, can they talk!  But, can they suffer?”

This magnificent passage set the tone for humanitarian action for prevention of cruelty to animals in the early part of the century. 

In 1811, Lord Erskine (1750-1823), in a speech before the House of Lords, portrayed the cruelties inflicted upon animals and asked for protective legislation. 

In 1821, Richard Martin, a land-owner of Galway, proposed a law to prevent the ill-treatment of horses.  The Bill was laughed out of the Commons.  In the next year he secured the passage of the Ill-treatment of Cattle Bill.  It prohibited the cruel treatment of cattle and for persons who wantonly and cruelly beat, abused or ill-treated any horse, mare, ox, sheep or other cattle it provided for the imposition of a fine of five pounds or imprisonment for three months.

There was however nobody to enforce the legislation.  Martin and a number of notable humanitarians formed a Society on 16 June 1824 which had as its immediate purpose the gathering of evidence of the maltreatment of animals.  Among the first members were the evangelicals William Wilberforce and Thomas Fowell Buxton.  This Society later became the Royal Society for the Prevention of Cruelty to Animals, being designated ‘Royal’ by Queen Victoria in 1840.  It became the leader in campaigns against brutal sports, experimentation and other forms of cruelty to animals.

It was also this Society which set up the National Society for the Prevention of Cruelty to Children.  Cruelty to children first became an active issue in New York in the Mary Ellen case (1874).  In that case a foster mother could not be punished or restrained.  The child had to be rescued under the Cruelty to Animals Act which was legislation modelled on the English legislation.  In England the Prevention of Cruelty to Animals Association campaigned for separate legislation to protect children.  In 1884 the first Prevention of Cruelty to Children legislation was enacted in England.  In the same year the National Society for Prevention of Cruelty to Children was established.

The Animal Prevention Society campaigned for improved cruelty to animals legislation, building on that of the 1822 Act.  In 1849 the Cruelty to Animals Act imposed forfeiture and penalties for the ill-treatment of animals.  This law, together with the 1854 amendment, became the foundation of all future legislation in England and the model for other common law countries.  In 1876, further legislation specifically extended the Cruelty to Animals Act to experimentation upon animals for scientific purposes, where the animal is alive and the experiments are calculated to inflict pain.  Subsequent legislation regulated vivisection requiring it to take place at a registered place and for an approved purpose.  The failure of the United States to enact comparable legislation has resulted in horrific treatment of animals in the course of experimentation on animals, recounted by Peter Singer in the second chapter of his work ‘Animal Liberation’.

What Bentham achieved was much more than legislation.  Over the course of the next century there was a revolution in social attitudes throughout the European world to the treatment of animals.  Henceforward cruelty to animals would occur but it was never defended.  It became recognised that the deliberate or unnecessary infliction of pain upon animals was wrong.

Nevertheless, and despite this achievement, the Benthamite position on animals was curiously incomplete.  It is clear that animals are entities of some moral significance or else they would have continued to be treated, in accordance with European thought, as mere adjuncts to human advantage or even amusement.  But was that moral significance restricted to their capacity, as sensate beings, to experience pain and pleasure?

Bentham himself seems not to have taken it further.  In the case of meat-eating he applied the utilitarian test and reached the dubious conclusion that animals did not suffer in the course of being killed for human food and therefore the eating of animal meat was ethically acceptable.

Bentham broke through the prevailing catholic view that some rigid and a priori ‘fence’ separated human and non-human animals and revolutionised western attitudes.  That animals possessed moral significance was a new idea.  Benthamite humanitarian attitudes were increasingly absorbed so that today we no longer question that cruelty to animals is wrong.

Professor Peter Singer has carried forward Bentham’s approach and articulated a comprehensive philosophy on the treatment of animals.

His starting point is the principle of equality which he says applies impartially to both humans and animals.  The principle of equality is not a proposition of fact.  It does not say that animals and humans are in fact equal.  It is a moral principle.  It relates to equality of moral significance.  Thus, in the case of human beings, we discard as irrelevant such differences as that one is black and another white or inequalities between us in intelligence or physical capacity.

Singer concludes that the critical question in determining moral significance is the capacity to experience pain and pleasure.  Once that exists the principle of equality applies impartially whether the entities concerned be human or non-human animal.  As Singer expresses it, ‘no matter what the nature of the being the principle of equality requires that its suffering be counted equally … the limit of sentience is the only defensible boundary of concern for the interests of others’.

Singer explains that this does not mean the principle requires that human beings and animals be treated identically when each is placed in the same situation.  Their legitimate interests may not be the same.  ‘If, for example, we had to choose between saving the life of an animal and that of a human being we will ordinarily choose the latter on the basis of characteristics that normal human beings have … Thus a normal human being has a heightened self-awareness and ability to plan for the future’ - giving him or her interests lacking in an animal.

What the principle requires therefore is that there should not be a different outcome just because one is ‘human’ and another is ‘animal’.  Both must be accorded equal consideration of their interests.*

The application of the principle is considered by Singer in the case of a mentally retarded child.  ‘The case against killing is strong, as strong in the case of some non-human animals (which) appear to be rational and self-conscious, considering themselves as distinct beings with a past and a future as the case against killing permanently disabled human beings at a similar mental level … The strong case against killing can be invoked against the slaughter of chimpanzees, gorillas and orangutans.’

As this illustration shows, the interests of an entity are tied to his or her capacity to experience.  That alone is the variable which may extend or delimit interests.  Thus ‘the more highly developed the conscious life of a being, the greater the degrees of self-awareness and rationality the broader the range of possible consequences’ (italics added).  In other words, non-sensate characteristics are only relevant in that they may indirectly stretch or contract an experience of pleasure or pain.

It also follows that ‘if a being is not capable of suffering, or of experiencing enjoyment or happiness there is nothing to be taken into account.  That is why the limit of sentience (using that term as a convenient if not strictly accurate shorthand for the capacity to suffer and/or experience enjoyment or happiness) is the only defensible boundary of concern for the interests of others.  To mark this boundary by some characteristic like intelligence or rationality would be to mark it in an arbitrary way’.

The proposition that ethics is bounded by pleasure/suffering in this way assumes that the only ‘value’ an entity has are in its feelings or wants.  It follows that life per se has no value.  Ethics would only condemn the taking of life, if, and insofar as, that involves suffering or the deprivation of anticipated pleasure.

Such then are Professor Singer’s views.  Let us begin our consideration with the principle of equality and, in particular, the proposition that moral significance is to be equated with and limited by capacity to experience pleasure and suffering.  The question, we have to remember, is whether that capacity is the exclusive criterion.

Human beings are distinguishable from non-human animals by their having certain additional characteristics.  These include capacity to reason and exercise foresight; capacity to choose autonomously the conduct of their lives independently of mere reflex response to immediate sensation and capacity to create and experience beauty.

It is evident that if these ‘capacities’ in themselves do give rise to moral significance, human and non-human animals are not equal in moral significance.

It is these peculiarly human attributes of creative potential autonomy and moral responsibility that have produced the vast and complex evolution of human culture.  Ethical responsibility is itself an aspect of that culture.  It is the creation of this culture, by virtue of the ‘capacities’ we have described, that has elevated the functions of human beings above physical survival and reproduction of the species.

The moral outrage when it was learnt that Hitler had intended the obliteration of Paris; the revulsion felt when a Michaelangelo statue in the St. Peters was defaced; the international action taken when Florence was flooded and to prevent the erosion of the Parthenon or the subsidence of Venice, all bear witness to the ‘value’ we put upon human culture.  To suggest that this is only to preserve our own ‘enjoyment or happiness’ or that of future generations, seems forced and untrue.

If, however, civilisation has ‘value’, moral significance must be accorded to the ‘capacities’ which have enabled it to have been produced.   Human beings and animals are, it would seem, of unequal moral significance.  In his work ‘On Aggression’ Konrad Lorenz brings out rhetorically perhaps, but also effectively, the gradations in moral significance of the different forms of life.

“That the origin of a higher form of life means an increase in value is a reality as undeniable as our own existence.  Try - only in imagination - to kill in succession a lettuce, a fly, a frog, a guinea pig, a cat, a dog, a chimpanzee (you) will be aware how difficult murder becomes as the victim’s level of organisation rises ... the degree of inhibition of killing each one of these beings is a very precise measure for the considerably different value we cannot help attributing to lower forms of life”.

What then are the ethical duties of human beings to animals?

It is necessary to be clear that we are speaking of are duties human beings owe.  Animals do not hold rights and cannot do so.  ‘Rights’ imply a choice whether they will or will not be exercised.  We, humans, may commit wrongs to animals.  There are no correlative rights.

First, we can agree with Singer, and Bentham before him, that animals possess moral significance and that their capacity to experience suffering is a primary reason for that.  We see in animal suffering precisely the same sensation as humans experience.  We identify with the suffering animal.  If the suffering of a human being evokes a reaction of sympathy so does that of an animal.·

But the foundation of our duties to animals also rests upon wider and less intuitive considerations.  Like us animals belong to an evolutionary continuum which is not broken by any differences between humans and animals.  When Bentham wrote - more than a quarter of a century before publication of the ‘On the Origin of Species’ - it was generally believed that the human and animal species had been separately created.  We now know that they evolved from a single source and are patterned on the same life substance, D.N.A.  As Darwin wrote in the final pages of his great work, ‘all living forms of life are the lineal descendants of those who lived long before the Cambrian epoch’.  In ‘The Descent of Man’ (1871) this idea was developed further when he said that ‘the various emotions and faculties … may be found incipient in the lower animals’.  At the cognitive level we thus recognise that humans and animals belong to life which is larger than either of them.  At the same time we see in each animal the same needs for existence and the same ‘will to live’ as we experience.  In the higher animals we see the same parental protection of the young and the same fear of death.

It is from this commonality that we derive our moral duties to animals.  The infliction of pain unaccompanied by human use or purpose, is cruelty.  We may add in the light of our analysis that humans are under a positive duty to protect and care for animals at least where no contrary human purpose is involved.

More difficult questions arise where we seek to use animals for human purposes.  What duties lie upon us in those circumstances?

Here we come to the Kantian rule which forbids the use of human beings as means because each human being is an end.  Professor Singer has drawn upon this to ask, ‘if possessing a higher degree of intelligence does not entitle one human being to use another for his own ends, how can it entitle humans to exploit non-humans for their own purposes?’

To disentangle this, we need to recognise that the Kantian rule, as applied to humans, is too absolute.  Wherever specialisation exists, human beings are used to satisfy the purposes of society.  Such use is not unethical and may be beneficial.  A weaker proposition may however be justified that the moral significance of human beings must be respected when they are used and in their use, and the failure to do so will result in the use being wrongful.  It follows that an ethical onus lies upon us to justify the use of another for our ends.  Such an onus may be discharged.  Thus, there may be true consent, reciprocal benefits and general equity.  At the same time, the ‘use’ and the ‘end’ must themselves be ethically acceptable.

Animals have, as we have said, moral significance (although in certain respects unequal to that of human beings).  It follows that that significance must be respected in their use by us.   One important consideration is that animals cannot consent to the way in which they are used.  This in itself requires that the kind of use to which they are put should be scrutinised carefully and objectively.

In the light of this, the general criterion would seem to be that animals may be used for human purposes where the end is ethically acceptable and the use is, in a practical sense, necessary.  ‘Whenever I injure life of any sort, I must be clear whether it is necessary’, Albert Schweizer.*

The end must be justifiable and significant.  Thus neither Game shooting nor Bull Fighting could, for this reason, be justified.  Indeed, these activities would at best seem to hover on the edge of cruelty.

The means must, as we have said, be necessary.  Necessity though cannot be defined by any hard and fast rule.  Circumstances may differ historically.  Thus the hunting stage of human culture almost necessarily involved the killing of animals for food.  It may be doubted whether in any practical sense primitive societies could have survived otherwise.

By about 4000 BC in certain areas, somewhat later in others, domestication of cattle had begun.  The use of animals in agriculture was advanced by the discovery of the wheel.  It is hardly too much to say that the whole edifice of cultural development from neolithic times until the industrial revolution - the product of human creativity - has depended very largely upon the human use of animals.

From these kinds of ‘uses’ we must go to the killing of animals for human purposes in modern western society.  Our remarks apply to the higher kind of animals.

First, to what extent would human survival justify the taking of animal life?  Let us test it by an extreme illustration.  Suppose that an air accident has occurred in which all the passengers are killed except for a man, a woman and a dog.  The wrecked aircraft is icebound.  Radio contact is eventually made and through it the survivors learn that rescue cannot take place for at least two weeks.  It is not possible, given the absence of food and their weakened condition, for all three - the man, the woman and the dog - to survive that period.  Two may survive but only if one is killed and eaten.  We would have little difficulty in deciding upon the relative value of each.  Obviously, the dog’s life should be taken.*

However, in a modern industrial society we are under no such constraints and, except in the case of certain ill human beings, meat is not necessary for health.  Whatever may have been the position in the past or in some unusual situations today, there is ordinarily no practical necessity for meat to be eaten.  Whilst the principle of equality has nothing to do with it, we may agree with Peter Singer that ‘it would be better to reject altogether the killing of animals for food, unless one must do so to survive.  Killing animals for food makes us think of them as objects that we can use as we please.  Their lives count for little when weighed against our mere wants.*

The greater the harm to animal life in any proposed use the greater must be the human need to justify it.  We may consider this in relation to animal experimentation.  Any unreflective assumption that animal experimentation is always justifiable is dispelled by Professor Singer’s horrific account, in the second chapter of ‘Animal Liberation’, in which he describes animal experimentation in the United States.

Let us turn to a case which might appear justifiable – that of poliomyelitis.  Professor Macfarlane Burnett said that the Salk vaccine, which eradicated that disease, would never have been discovered but for experimentation on monkeys.  And yet in that process monkeys suffered and were killed.

Professor Singer would probably accept the ethical justification for this experimentation if appropriately controlled and limited.  He would do so upon the basis of equal consideration being given to the suffering of the monkeys (through the experiments) and to humans (should those experiments not have been carried out).  Such a balancing test to give effect to the principle of equality does however seem contrived.  It is given apparent plausibility in this instance only by the successful outcome of the experiments.

It is more straightforward to start any analysis by acknowledging that the preservation of human life and the avoidance of crippling disease is of greater value than the preservation of animal life.  Save in exceptional circumstances, it is wrong to inflict suffering upon monkeys.  Only because poliomyelitis is such a dread disease could such suffering by the monkeys, as was unavoidable, be justified.  The analysis differs from Professor Singer’s reliance upon the principle of equality but it would seem that the practical steps to be taken would not differ greatly from those stated by him in ‘Animal Liberation’.  He would require that ‘no experiment be concluded without prior approval of an Ethics Committee, including Animal Welfare representatives, authorised to refuse approval to experiments that it does not consider the potential benefits outweigh the harm to animals’.*



*           Ulpian, a Roman Jurist, who was referred to in Justinian’s Code, suggested that natural law derived from instincts common to humans and animals.  This ‘unlucky’ phrase, as Pollock described it, may have been influenced by the Pythagoreans who saw no division between Man and animals.  The comment became incorporated into the Institutes.  It was however totally out of accord with stoic teaching on natural law, Vinogradoff, Common-sense in Law, H.U.L. p.236.


*           Dictionnaire Philosophique.


*           See generally, ‘All Animals are Equal’, Applied Ethics, edited by Peter Singer, O.U.P., p.215.


·           We would now be repelled by Descartes’ mechanistic philosophy which held the ‘suffering’ of animals to be merely apparent and illusory.


*           Civilisation and Ethics, p.221.


*           English law does not recognise a defence of necessity to a charge of murder where human beings were involved and one was killed and eaten by the others to remain alive.  R v Dudley & Stephens ((1884) 14 Q.B.D. 273).


*           Practical Ethics.


*           None of the above should be taken as denying the moral principle of equality.  What is in question is its application in the case of animals. We respect each person’s life, each person’s autonomy and each person’s wish to avoid pain in the same way as that of every other human person and of our own.  We do not individualise moral significance upon the basis of individual differences such as prospective longevity, intellectual attainments or physical capacity.  Such differences are part of the human condition and are not relevant to the moral respect owed to each individual.  Accordingly, to humanity in general the principle of equality applies.  Nevertheless, differences may affect the duties owed.  We respect a child as a human person but place restrictions upon his or her autonomy.  Our respect for the right to life and avoidance of suffering extend to the mentally retarded child or to an older person suffering from Alzheimer’s disease.  We recognise in the case of each the need for greater care.  We do not distinguish them from other sick persons because they lack the capacity to exercise autonomy.


            Professor Singer seeks to equate the moral significance of a mentally retarded child with that of the higher animals.  He suggests, on this account, that our duty to respect their lives is the same in each case.  It is probably true that their ability to exercise autonomy is not materially different.  But our moral duty necessarily differs in the case of an entity naturally lacking that autonomy and one abnormally deprived of it.  The duty to look after and to provide compassionate care in the one case, because of deprivation, does not arise in the case of the other.