Animal Rights and the Wrongness of Killing

7. Lives Killed vs Utility Lost

In the previous section, I argued that if all other circumstances are kept the same, it is worse to kill a happy human being than it is to kill a happy animal. The question arises: Is it also worse to kill a happy human being than it is to kill a large number of happy animals, other things being equal? Is there some number of lives of happy animals whose loss would outweigh the loss of one happy human being, other things being equal? If we had accepted the 'total' view maximizing principle, this answer would always be in the affirmative, irrespective of the species of sentient animal considered. All that would be required for the balance to weigh in favour of the animals is that the sum of utility lost through their deaths be greater than the utility of the life of the human being.

As we saw in §5.1 above, the 'total' view cannot avoid the 'Repugnant Conclusion' and must therefore be rejected. I had also found the 'average' view wanting. You may think that the 'prior existence' view will give us a convincing answer to our question. This view was devised specifically to overcome the intractable problems with the 'total' view and 'average' view. On this view, our only obligation is to maximize the aggregate utility of beings that exist, or will exist, independently of the act or rule under consideration. To its detriment, this view also suffers from a repugnant conclusion. And that is that it implies the counterintuitive conclusion that if it were possible to create a number of very happy beings ex nihilo, and at no cost in utility to the creator, then the creator would have done nothing wrong if they had refrained from creating these beings. This conclusion runs counter to the central idea underlying utilitarianism.[14]

Diagram 7 – Comparing human lives with chicken lives

Block diagram displaying utilities of populations A, B and C

In contrast, the 'mixed' view maximizing principle developed in this essay provides us with a very different answer; one that is both moderate and intuitively appealing. The answer that it gives is that where the average utility of the lives of the animals killed is below a certain threshold (namely 0·7ay where, in this case, ay is the utility of the life of the human being), then no number of lives of these animals will outweigh the value of a single human life.

This is best illustrated using the scenario pictured previously in Diagram 4 in §5.4 above. The diagram is reproduced above as Diagram 7. In this scenario, I will contrast the moral seriousness of the killing of one human being with that of killing 200 chickens. Putting flesh to this example, let us say that segments b and d in population C is a sub-population consisting of 10 very happy human beings, each with a utility of 10 units. Let us say further that segment c in the same population is a sub-population of 200 very happy chickens, each with a utility of 3 units. (Whether the utility value of 3 units actually does or does not correspond to the utility of a very happy chicken will not affect the point I am trying to make here.)

Consider now alternative populations A and B. Population A is what is left if the 200 chickens in population C are killed. Population B is the population remaining following the killing of one of the human beings in population C. To ensure that we are only evaluating the utilities of the lives lost, without considering side-effects, we must stipulate that the killing of the chickens in the one case and the killing of the human being in the other affects the utility of no other being. In this sense, the depiction of populations A and B in Diagram 7 above assumes all other things are equal leading up to and following the killings.

As we saw in §5.4, applying the 'mixed' view utilitarian calculus to this scenario led to the conclusion that population B is less morally preferable compared with population A. So, the 'mixed' view maximizing principle confirms our intuition that it is worse to kill the single human being (leading to population B) than it is to kill the 200 chickens (leading to population A). And we reached this conclusion in spite of the fact that the total utility of the 200 chickens (200 × 3 = 600 units) is of far greater magnitude than the total utility of the single human being (1 × 10 = 10 units). The 'mixed' view maximizing principle, in contrast with the 'total' view, enjoins us to maximize mixed utility. Comparing mixed utilities using the calculations completed in §5.4 above, we can confirm that the mixed utility of the single human being is 100 units while the mixed utility of the 200 chickens is less at 94.7 units.

The heavy lifting in contrasting the value of a single human life with that of many chickens is done by Equation 2 in §5.2 above. What this equation signifies is that where the individual utilities of the animals to be compared are less than 0.7 that of the utility of a human being, then no number of such animals will outweigh the mixed utility of that single human being. As the number of animals considered increases, Equation 2 ensures that their mixed utility asymptotically approaches the mixed utility of the human being. The important point to note here is that this contrast in value not only applies to the comparison between the lives of human beings and the lives of animals, but also more generally to the comparison between any two classes of sentient beings. Human beings have no special privilege in this regard.

Looking at the other side of the coin, if the animal lives to be compared with human lives have average utilities of greater than or equal to 0.7 that of the utilities of the human lives, then there will exist some finite number of animal lives whose loss will be greater than the loss of some specified number of human lives, other things being equal. The difficulty lies in discovering where this threshold of average utility is located on the scale of neurophysiological complexity. For example, can the value of the life of a normal, happy human being be outweighed by the value of some number of lives of normal, happy chickens? If not, then what of the lives of zebras or dogs or chimpanzees? I am confident that the threshold cannot be as low as the level of chickens, or even dogs. I am inclined to place it at the level of chimpanzees, whales and dolphins, for these higher-order mammals have a level of sentience and richness of life somewhat comparable to normal human beings.[15]

It may be objected that the utility of the life of a normal, happy chimpanzee, whale or dolphin is not 0.7 that of a human being. I am inclined to think that this proportion cannot be far off the mark. This objection amply illustrates the observation that talk of abstract units of happiness is not as useful as direct comparisons of the relative worth of individual lives. What I mean by this is that in discussions of this sort, it may be more productive at this stage to try and reach agreement on how many happy lives of the members of a given sentient species will outweigh the life of a happy human being. I suspect this approach may be more useful than trying to place the lives of the members of each species on a scale of worth ranging from 1 to 10.

A related objection is that no animal can have a life that is comparable in richness and variety to that of a normal, happy human. Observing the natural curiosity, the depth of emotional responses and the intricate social behaviour of chimpanzees, whales and dolphins, I find this difficult to accept. A consequence of this objection is that the lives of one million happy chimpanzees are not more valuable than the life of a single normal, happy human being (other things being equal). Given the current state of ethology, I find this view most unpalatable.

What I have been doing here is offering my impressions. This highly complex and difficult question about the relative values of different animal lives, both human and non-human, requires much more thought and discussion. We ought not be surprised by the difficulty of the task at hand. It is only during the last few decades that the view that animal lives have value in their own right is being accepted as an ethical stance requiring serious consideration.


  1. [14] See my Allan [2015: §5] for a fuller discussion of this criticism.
  2. [15] See, for example, Goodall [1971: ch. 19] and Jenkins [1976].

Copyright © 2015

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