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Is it Wrong to Kill
Non-Human Animals?
I
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Peter Singer: “All Animals are Equal ”
Singer’s Project
• Singer argues we should “extend to other species the basic
principle of equality that most of us recognize should be
extended to members of our own species.” (401)
• As such, we need to curtail the use of animals in experiments
(medical or otherwise).
• As well, if we are going to eat meat, we need to minimize the
suffering of animals in the food industry.
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Singer’s Central Argument
P1 Beings have interests just in case they are capable of
suffering. (404)
P2 Human beings and many non-human animals are capable
of suffering.
P3 Therefore, human beings and many non-human animals
have interests.
P4 Basic Principle of Equality: “[T]he interests of every being
[…] are to be taken into account and given the same
weight as the interests of any other being.” (403)
P5 Human beings and many non-human animals have an
interest in avoiding suffering.
C Therefore, the interests non-human animals have in
avoiding suffering is to be given the same weight as the
interests human beings have in avoiding suffering.
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Equality & Discrimination
• A liberation movement demands an expansion of our moral
horizons and an extension or reinterpretation of the “basic
moral principle of equality”.
 Race
 Orientation
 Sex
• Practices previously regarded as natural and inevitable come
to be seen as being based on an unjustifiable prejudice.
• We should make the same mental switch in our attitudes and
practices towards non-human animals, extending to other
species the same principle of equality that we recognize
should be extended to members of our own species.
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Wollstonecroft & Taylor
• Mary Wollstonecraft’s 1792 book, Vindication of the Rights of
Women, was widely regarded as absurd.
• Thomas Taylor responds with an anonymous satire, A
Vindication of the Rights of Brutes, in which he tries to show
that the arguments supplied by Wollstonecraft, if sound, are
equally sound when applied to non-human animals.
 But, Taylor argues, that “brutes” have equal rights to men
is patently absurd.
 If the argument leading to the conclusion that non-human
animals have rights equal to men is unsound, then so too
is Wollstonecraft’s argument, since the same argument is
used in each case.
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Capacities & Rights
• Might we respond to Taylor, that the reason women have an
equal right to men, but that non-human animals do not, is
that women and men have certain capacities that non-human
animals do not, such as the ability to make rational
decisions?
 In other words, men and women are similar and so should
have equal rights, while humans and nonhumans are
different and so should not have equal rights.
• Certainly, biologically, men and women have different
capacities, and these may lead to different rights.
 Likewise, since a pig isn’t capable of voting, it shouldn’t
have the right to vote.
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Equality Does Not Imply Sameness
• “The extension of the basic principle of equality from one
group to another does not imply that we must treat both
groups in exactly the same way, or grant exactly the same
rights to both groups.” (401)
• Rather, the sort of equality we should be concerned with is
equality of consideration, and equal consideration for
different beings may lead to different treatments and different
rights.
• Certainly, humans come in all sorts of sizes and shapes, with
differing moral capacities, intellectual abilities, sensitivities,
capacities to experience pain and pleasure, and so on.
 If the demand for equality were based on some actual
equality of all human beings, we would have to stop
demanding equality.
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Equality Does Not Imply Sameness
• “Although humans differ as individuals in various ways, there
are no differences between the races and sexes as such.”
(402)
 A person’s race or sex is no guide to his or her abilities.
• So far as actual abilities are concerned, there do seem to be
some measurable differences between races and sexes,
when taken on average.
 What we don’t know is how much of this difference is due
to genetic endowments, and how much to environmental
differences.
 But it would be dangerous to rest a case against racism
and sexism on the belief that all significant differences are
environmental in origin: if there did turn out to be some
genetic basis for differences in ability, racism and sexism
would in some way be defensible.
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Equality Does Not Imply Sameness
• There is a stronger argument to be made for equality for the
races and sexes – one which does not depend upon
intelligence, moral capacity, physical strength, or other
matters of fact.
 Equality is a moral ideal and not a simple assertion of fact.
 There is no compelling reason for assuming any factual
difference in ability between two people justifies any
difference in the amount of consideration we give to
satisfying their needs and interests.
 The principle of the equality of human beings is not
descriptive of their actual equality, but prescriptive of how
we should treat them.
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Equal Consideration of Interests
• To treat another being as equal to another means to give
both beings equal consideration for their interests.
• “The capacity for suffering and enjoying things is a
prerequisite for having interests at all, a condition that must
be satisfied before we can speak of interests in a meaningful
way.” (404)
I can suffer, so I
I can’t suffer, so I
can have interests.
can’t have interests.
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Suffering, Sentience, and Speciesism
• If a being can suffer, there can be no justification for not
taking that suffering into consideration.
 “No matter what the nature of the being, the principle of
equality requires that its suffering be counted equally with
the like suffering—in so far as rough comparisons can be
made—of any other being.” (404)
 Sentience—the capacity to suffer or experience
enjoyment—is the only defensible boundary of concern for
the interests of others.
• Racism violates the principle of equality by giving greater
weight to the interests of members of one’s own race.
• Likewise, speciesism violates the principle of equality by
giving greater weight to the interests of members of one’s
own species.
• “Most human beings are speciesists.” (404)
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Suffering, Sentience, and Speciesism
• We tend to regard the lives of non-human animals as a
means to an end: we eat them.
• But we don’t need to eat animals, certainly not on the
grounds of satisfying nutritional needs.
• An even clearer indication of our speciesism is the suffering
we inflict on non-human animals while they are alive before
we eat them.
• None of these practices cater to any more than our tastes.
• “To avoid speciesism we must stop this practice, and each of
us has a moral obligation to cease supporting this practice.”
(405)
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Non-Human Experimentation
• The same form of discrimination is apparent in the
widespread practice of experimentation on other species to
ascertain if some substances are safe for human beings, or
what effect some stimulus will have.
 If an experimenter is not prepared to experiment on a
newborn infant, he should likewise refrain from
experimenting on adult non-human mammals.
 If anything, adult non-human mammals are more aware,
and is at least as sensitive to pain as a newborn infant.
 Certainly, we should be more prepared to experiment on
brain-dead human beings than healthy, adult non-human
animals.
• The experimenter shows his speciesism by experimenting on
a non-human animal where he would not perform the same
experiment on a human at an equal or lower level of
sentience.
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Non-Human Experimentation
• If humans are to be regarded as equal to one another, then
we need some sense of “equal” that does not require any
actual equality of capacities, talents, or other factual
characteristics.
• If, on the other hand, we are to regard “all humans are equal”
as a non-factual (perhaps prescriptive) statement, it is even
more difficult to exclude non-humans from the sphere of
equality.
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Singer’s Central Argument Revisited
P1 Beings have interests just in case they are capable of
suffering. (404)
P2 Human beings and many non-human animals are capable
of suffering.
P3 Therefore, human beings and many non-human animals
have interests.
P4 Basic Principle of Equality: “[T]he interests of every being
[…] are to be taken into account and given the same
weight as the interests of any other being.” (403)
P5 Human beings and many non-human animals have an
interest in avoiding suffering.
C Therefore, the interests non-human animals have in
avoiding suffering is to be given the same weight as the
interests human beings have in avoiding suffering.
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Singer’s Central Argument Revisited
P1 Beings have interests just in case they are capable of
suffering.
 Might a being have interests and yet be incapable
of suffering?
P2 Human beings and many non-human animals are capable
of suffering.
 Certainly, there are borderline cases, but certainly
this clearly applies to dogs, and cats, and cows,
and chickens, and…
P3 Therefore, human beings and many non-human animals
have interests.
 Follows from P1 and P2.
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Singer’s Central Argument Revisited
P4 Basic Principle of Equality: “[T]he interests of every being
[…] are to be taken into account and given the same
weight as the interests of any other being.”
 There are multiple ways that the Basic Principle
might be violated: racism, sexism, speciesism...
 According to Singer’s argument, humans in
persistent vegetative states do not have interests,
and so the Basic Principle does not apply to them.
P5 Human beings and many non-human animals have an
interest in avoiding suffering.
 Implicit in the above argument.
C
Therefore, the interests non-human animals have in
avoiding suffering is to be given the same weight as the
interests human beings have in avoiding suffering.