Animal Rights and the Wrongness of Killing

4. Duties and Sentience

In my Allan [2015: §3], I argued that in thinking about how we ought to act, we first need to divest ourselves of spurious metaphysical notions. These mistaken meta-ethical presuppositions that we need to avoid include notions that we ought obey the strictures of some supposed divine being, that we somehow intuit synthetic a priori constraints on our behaviour and that we are governed by some natural law. I argued that what underpins the ideal of objectivity in ethical discourse is not supernatural entities or supervenient properties, but the principle of impartiality. On this view, for a person to be objective in an ethical sense, they need to consider the interests of each party on an equal footing, irrespective of the identity of the interest holder.

Book cover: Causing Death and Saving Lives by Jonathan Glover

This principle of impartiality seems to drive us to a consequentialist view of moral action; that the right thing to do is to maximize the satisfaction of interests without fear or favour. By tying this theory of duty to the theory of value elucidated above, we are now in a position to answer the question, 'To what kinds of beings do we owe obligations?' The answer is that for a being to demand our ethical concerns, it matters not whether they can make claims, enter into social contracts, possesses rationality or display autonomy. What matters is whether they have desires or preferences. From the above considerations, whether they can sense pain or see red is also morally irrelevant. A being is part of the moral landscape only if it can matter to them what conscious states they are in; that is, only if they have a conative life. Let us say that a being that has such a conative life is 'sentient'.[8]

What kinds of beings possess such a capacity for sentience? The most current evolutionary and neurophysiological evidence indicates that the border between those creatures with affective states and those without roughly corresponds to the distinction between vertebrates and invertebrates.[9] On utilitarian grounds, then, if utility is satisfaction and that which promotes satisfaction, we can have no direct duties to avoid killing invertebrates and plants.

In saying that we do not have a direct duty in these cases, let me clarify what I mean by 'direct duty'. A direct duty to treat an entity in a certain way is a duty owed to the entity itself. In contrast, an indirect duty is a duty to treat an entity in a certain way that derives from a duty owed to another. In this latter case, the duty is not owed to the entity itself. For example, although I have a direct duty not to kill my neighbour, I only have an indirect duty not to steal his car. The latter duty is indirect because this duty is not owed to his car but to my neighbour.

Applying this distinction to the killing of invertebrates and plants, we have a duty not to end their lives only when to kill them would result in a diminishing of net satisfaction for creatures with a conative life. To extend our direct duties to non-sentient entities in a way that would not simply be a token gesture would be to encroach on the interests of creatures with a conative life. I cannot see how such an extension could be morally justified, considering that what happens to a tree or jellyfish matters not one iota to the tree or jellyfish. It may matter a great deal, however, to some sentient creature. Conservation of the natural environment has, I think, more than adequate justification by appealing to our global and national interests, the interests of conservationists and the interests of non-human vertebrates. Such a justification is compelling without recourse to an ethic of the environment, although this is not the place to argue this point here.[10]

Could it be the case that the wrongness of killing lies in factors that are wholly or partly independent of the consequences for the existence of intrinsic goods? Could it be that consequentialism is mistaken? In my Allan [2015], I critically review deontic theories of the wrongness of killing and find them wanting. I will proceed here on the basis that whenever killing is wrong, it is because of the consequences it has for the happiness and sufferings of sentient creatures.


  1. [8] This usage of the term 'sentient' is not strictly correct. However, because of the lack of a suitable substitute in the English vocabulary, it has been increasingly used in this way. I shall follow this deviant practice.
  1. [9] See Melzack [1973: ch. 4]; Singer [1976: 29–33; 1979c: 60f] and Sumner [1981: 143–7].
  1. [10] On the global predicament resulting from our current rate of natural resource depletion, see the important work of the Club of Rome in Meadows et al [1974]. For a utilitarian critique of the possibility of an environmental ethic, see Frey [1983: ch. 14].

Copyright © 2015

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