THEORY
Conversely, a mouse does have an interest in not being treated in this way
because it will suffer. Singer argues that the principle of equal consideration
of interests should consequently be applied to all creatures that can suffer:
sentience ‘is the only defensible boundary of concern for the interests of
others’ (ibid.: 50). Singer’s definition of sentience includes a range of life-
formssuch as birds, reptiles, fish and some crustaceans, drawing the line
‘somewhere between a shrimp and an oyster’ (Singer 1976 :188).
Regan ( 1983 )develops a rights-based approach to animal protection. All
‘subjects-of-a-life’ – individuals who have beliefs, desires, perception, mem-
ory and a sense of the future, an emotional life and a psychophysical identity
over time (p. 243) – are either ‘moral agents’ or ‘moral patients’ possessing
equal intrinsic value.^12 Thus he extends the moral community from humans
to include many animals. Everyone within that moral community is enti-
tled to respectful treatment. Just as human moral agents should respect the
rights of, and have a prima-facie duty not to harm, individual human moral
patients (the handicapped, senile and infants), so individual non-human
moral patients (mentally normal mammals over the age of one year) have
an inviolable right to be treated with respect and allowed to ‘live well’.
Thus animal liberationists differ from holists in two important respects.
First, theyextend the moral community to include a range of sentient crea-
tures, but they do not venture as far into nature as the holists. Secondly,
both Singer and Regan focus on the intrinsic value that resides in the capac-
ities and interests ofindividualcreatures rather than in wholes (ecosystems,
species). The key difference between the two writers is that Singer employs
utilitarianism whereas Regan uses a rights-based argument. The work of
both writers has been subjected to extensive review and, for reasons of
space, the following critical discussion focuses on the writings of Singer
as probably the best-known exponent of animal liberationism.^13
Singer’s argument is vulnerable to some of the familiar criticisms of util-
itarianism. Although animal liberation is concerned with the welfare of
individual animals, ironically one weakness of utilitarianism is that it is
not always very good at defending the individual (Williams 1973 ). A conse-
quentialist argument such as utilitarianism places intrinsic value only in
‘states of affairs’ – suffering or enjoyment – rather than in the individuals
who are experiencing that suffering or enjoyment. So the principle of max-
imising aggregate pleasures over pains in a given population of individuals
might result in significant harm being inflicted on one or two individuals
in order to improve the net welfare of a larger group of individuals. Hence
utilitarian calculations may provide the individual creature with only a lim-
ited, rather than an absolute, obligation that its interests be respected by
humans.
Adifferent response is to reject sentience as a sufficient criterion to be
arights-holder, or to receive equal consideration, and instead to argue that
other attributes, notably the ability to reason or to talk, set humans apart
from other species. Many political philosophers argue that the inability to