Last Man Arguments
Published in The Encyclopedia of Environmental Ethics and Philosophy 2 Vols
(ed) J. Baird Callicott. New York: Macmillan, 2009, Vol 2, pp. 40-41
by William Grey
The last man argument was devised by Richard Sylvan (before 1983 Richard Routley) and was first published in Routley (1973). It is a thought experiment designed to show that the prevailing principles of the dominant Western ethical tradition are unable to provide a satisfactory basis for an environmental ethic. An adequate ethic of concern for the non-human world must therefore have very different foundations.
The shared core assumptions of western ethics (which Sylvan calls a "super ethic") include a freedom principle, according to which agents are permitted to act as they please provided that they do not (1) harm others (understood usually, though not always, as other persons), or (2) harm themselves. Sylvan labelled this anthropocentric principle basic human chauvinism, because it affirms that only human interests and concerns feature in moral deliberation and choice. The last man thought experiment was devised to refute this basic core principle, and thus expose the inadequacy of traditional western ethics to support an environmental ethic.
Ethical principles must be universal and therefore apply not just to actual situations but to all possible situations. It is for this reason that thought experiments are important intuition pumps and play a central role in testing ethical principles. The last man thought experiment is as follows:
Holmes Rolston (1975) has set out a parallel 'African butterfly' argument in support of non-anthropocentric environmental values. Gratuitous acts of 'speciescide' carried out by unscrupulous butterfly collectors, like the actions of Sylvan's last man, are reprehensible to the environmentally enlightened conscience. Robin Attfield (1981) and Mary Anne Warren (1983) have also presented variants of the argument.
A thought experiment which anticipates some aspects of Sylvan's argument was proposed by G.E. Moore in a famous attempt to establish the objective value of beauty.
Value intuitions depend crucially on the nature of evaluators. It is not difficult—given our biologically programmed aversion to dung, and a clear adaptive advantage in avoiding it—to share Moore's intuition. However this preference is clearly shaped by our biological constitution. It is far from clear that our preference would be shared by, say, a dung beetle or a blowfly. Rather than establishing the objective value of beauty, Moore has established the existence of deep-seated aesthetic intuitions widely shared among humans—and the difficulty of thinking like a blowfly.
Sylvan's argument similarly fails to establish secure objective grounds for non-anthropocentric values. However like other famous thought experiments—such as brains in vats (Brueckner 2004) and "trolley" problems (Thomson 1976)—it helps us to regiment our intuitions. The powerful visceral impact of the last man thought experiment reveals a widespread, though sadly not universal, biophilia—an affinity for rich, diverse, complex and beautiful biological systems. The use of cyanide and explosives for fishing on coral reefs, rather than sustainable practices, and the clear-felling and burning of old growth forests, generate a similarly powerful visceral repugnance which is also widely shared but also, alas, not universal. The last man thought experiment helps us to appreciate that the depletion of biodiversity impoverishes not just the biosphere, but also the requirements for the sort of human life to which we are adapted and to which many of us aspire.
Bibliography
Attfield, Robin. 1981. The Good of Trees. Journal of Value Inquiry 15: 35-54
Brueckner, Tony. 2004. Brains in a Vat. The Stanford Encyclopedia of Philosophy, Winter 2004 Edition. Ed. Edward N. Zalta. URL =
Hume, David. 1740. A Treatise of Human Nature, Vol III. Ed. L.A. Selby-Bigge. Oxford: Clarendon Press, 1888
Moore, G.E. 1903. Principia Ethica. Cambridge University Press
Rolston III, Holmes. 1975. Is There an Ecological Ethic? Ethics 85: 93-109
Routley, Richard. 1973. Is There a Need for a New, an Environmental, Ethic? Proceedings of the XVth World Congress of Philosophy 1: 205-210
Routley, Richard and Val Routley. 1980. Human Chauvinism and Environmental Ethics. In Environmental Philosophy, ed. D.S. Mannison, M. McRobbie and R. Routley, 96-189. Canberra: Australian National University
Thomson, J. J. 1976. Killing, Letting Die, and the Trolley Problem. The Monist 59: 204-17
Warren, Mary Anne. 1983. The Rights of the Nonhuman World. In Environmental Philosophy: A Collection of Readings, ed. R. Elliot and A. Gare, 109-134. St Lucia: University of Queensland Press
The shared core assumptions of western ethics (which Sylvan calls a "super ethic") include a freedom principle, according to which agents are permitted to act as they please provided that they do not (1) harm others (understood usually, though not always, as other persons), or (2) harm themselves. Sylvan labelled this anthropocentric principle basic human chauvinism, because it affirms that only human interests and concerns feature in moral deliberation and choice. The last man thought experiment was devised to refute this basic core principle, and thus expose the inadequacy of traditional western ethics to support an environmental ethic.
Ethical principles must be universal and therefore apply not just to actual situations but to all possible situations. It is for this reason that thought experiments are important intuition pumps and play a central role in testing ethical principles. The last man thought experiment is as follows:
- The last man (or person) surviving the collapse of the world system lays about him, eliminating, as far as he can, every living thing, animal or plant (but painlessly if you like, as at the best abattoirs). What he does is quite permissible according to basic [human] chauvinism, but on environmental grounds what he does is wrong. (Routley 1973, 207f)
Holmes Rolston (1975) has set out a parallel 'African butterfly' argument in support of non-anthropocentric environmental values. Gratuitous acts of 'speciescide' carried out by unscrupulous butterfly collectors, like the actions of Sylvan's last man, are reprehensible to the environmentally enlightened conscience. Robin Attfield (1981) and Mary Anne Warren (1983) have also presented variants of the argument.
A thought experiment which anticipates some aspects of Sylvan's argument was proposed by G.E. Moore in a famous attempt to establish the objective value of beauty.
- Let us imagine one world exceedingly beautiful. Imagine it as beautiful as you can; put into it whatever on this earth you most admire—mountains, rivers, the sea; trees, and sunsets, stars and moon. Imagine these all combined in the most exquisite proportions, so that no one thing jars against another, but each contributes to increase the beauty of the whole. And then imagine the ugliest world you can possibly conceive. Imagine it simply one heap of filth, containing everything that is most disgusting to us, for whatever reason, and the whole, as far as may be, without one redeeming feature... The only thing we are not entitled to imagine is that any human being ever has or ever, by any possibility, can, live in either, can ever see and enjoy the beauty of the one or hate the foulness of the other. Well, even so, supposing them quite apart from any possible contemplation by human beings; still, is it irrational to hold that it is better that the beautiful world should exist, than the one which is ugly? (Moore 1903, Ch III, Section 50)
Value intuitions depend crucially on the nature of evaluators. It is not difficult—given our biologically programmed aversion to dung, and a clear adaptive advantage in avoiding it—to share Moore's intuition. However this preference is clearly shaped by our biological constitution. It is far from clear that our preference would be shared by, say, a dung beetle or a blowfly. Rather than establishing the objective value of beauty, Moore has established the existence of deep-seated aesthetic intuitions widely shared among humans—and the difficulty of thinking like a blowfly.
Sylvan's argument similarly fails to establish secure objective grounds for non-anthropocentric values. However like other famous thought experiments—such as brains in vats (Brueckner 2004) and "trolley" problems (Thomson 1976)—it helps us to regiment our intuitions. The powerful visceral impact of the last man thought experiment reveals a widespread, though sadly not universal, biophilia—an affinity for rich, diverse, complex and beautiful biological systems. The use of cyanide and explosives for fishing on coral reefs, rather than sustainable practices, and the clear-felling and burning of old growth forests, generate a similarly powerful visceral repugnance which is also widely shared but also, alas, not universal. The last man thought experiment helps us to appreciate that the depletion of biodiversity impoverishes not just the biosphere, but also the requirements for the sort of human life to which we are adapted and to which many of us aspire.
Bibliography
Attfield, Robin. 1981. The Good of Trees. Journal of Value Inquiry 15: 35-54
Brueckner, Tony. 2004. Brains in a Vat. The Stanford Encyclopedia of Philosophy, Winter 2004 Edition. Ed. Edward N. Zalta. URL =
Hume, David. 1740. A Treatise of Human Nature, Vol III. Ed. L.A. Selby-Bigge. Oxford: Clarendon Press, 1888
Moore, G.E. 1903. Principia Ethica. Cambridge University Press
Rolston III, Holmes. 1975. Is There an Ecological Ethic? Ethics 85: 93-109
Routley, Richard. 1973. Is There a Need for a New, an Environmental, Ethic? Proceedings of the XVth World Congress of Philosophy 1: 205-210
Routley, Richard and Val Routley. 1980. Human Chauvinism and Environmental Ethics. In Environmental Philosophy, ed. D.S. Mannison, M. McRobbie and R. Routley, 96-189. Canberra: Australian National University
Thomson, J. J. 1976. Killing, Letting Die, and the Trolley Problem. The Monist 59: 204-17
Warren, Mary Anne. 1983. The Rights of the Nonhuman World. In Environmental Philosophy: A Collection of Readings, ed. R. Elliot and A. Gare, 109-134. St Lucia: University of Queensland Press