Sustainability concerns the relationship between humans and their natural environment over time. But there are various ethical understandings of that relationship with quite different implications. Two popular accounts actually repudiate human interdependence with nature by either making human interests completely subservient to a sacred nature, or by making nature completely subservient to human interests. Gro Brundtland's famous definition points in the right direction by focussing on the goal of meeting humanitarian needs in the present and the future, but her picture of human interests is too narrow and technocratic. What we need is a definition that is humanistic without necessarily being human-centred.
I. Do no harm!
Perhaps the most popular understanding of sustainability in the context of environmental ethics is the maxim 'do no harm'. i.e. human activities should be restructured to avoid damaging natural ecosystems. The strong points of this account are twofold.
First, it forces us to acknowledge that human activity does cause a lot of harm. For example, even the so-called New Economy that is supposed to be all about weightless services and information, actually retains an enormous physical industrial sector that disrupts and pollutes natural ecosystems. Moreover, doing harm to the environment can come back to bite us: if adjusted for the damage caused by air and water pollution to human health and ecological services, GDP growth in some countries might actually be negative.
Second, it challenges our instinctive anthropocentricism. Man is the measure of all things - we can never leave our human perspective behind - but that doesn't mean that human evaluation of environments is limited to asking "what's in it for us?". We can bring a range of other perspectives to bear, such as asking "what do polar bears need to flourish" or admiring the intricate co-ordination of a bee colony independently of their use-value for human interests.
Nevertheless sustainability as 'do no harm' fails to be a morally convincing or practically plausible normative restriction on human activity. It is liable to fetishising aspects of the environment by dogmatically asserting that they have an intrinsic value that takes priority over human interests. But the intrinsic, human independent value of the environment is difficult to see, let alone the justification for its priority over human interests. Ecosystems for example are just contingent arrangements of various species in a competitive equilibrium, and the analogy to an economy is an interesting one. Like economies they change form and make-up depending on the different forces and elements they are subject to (climate, different species, soils, etc), and those are always changing, with or without human interference. If any particular ecosystem is intrinsically valuable, then they all are, whether deserts or spruce forests, and no one particular ecosystem can be any more valuable than others, except for non-intrinsic reasons, like being rare, beautiful, or useful to us (or to other species we care about, like Pandas' special bamboo). When one eco-system changes into another, whether as a result of human action or other causes, it's unclear what net harm 'to the environment' has really been done, but the form of the 'do no harm' principle considers all change as loss. A strict interpretation is so strongly conservative that it is incompatible with human existence, since it would require an ephemeral humanity that would float ghostlike above the earth without materially affecting it. That logic leads straight to the Voluntary Human Extinction Movement.
2. Maximise Resources for Future Generations
Another popular version considers the environment as a stock of resources and focuses on human inter-generational justice. i.e. making sure that we maintain the stock of resources that our grandchildren, or great-great-great-grandchildren might want to use. Here we have a straightforward constrained maximisation problem: how much can we consume now without restricting future generations' consumption possibilities? This implies that present consumption should be limited to renewable, preferably self-renewing, resources (i.e. not fossil fuels) that also do not destroy other resources (e.g. through climate change).
The advantages of this account over 'Do no harm' is that it avoids fetishising the environment since it concerns itself directly with human concerns, and it raises the important issue of the interests of future human-beings.
Nevertheless it still seems unduly conservative and restrictive in at least two senses: First, why only consider resources? and second, why only consider future generations?
Why should we only think about the environment in terms of resources? This seems to unnecessarily restrict how we can value its other aspects, such as beauty. Further, why is conserving resources so important? Because they are supposedly scarce while human wants are unlimited? There is a kind of Malthusian logic here in which constraints are taken to be absolute (almost theological) before which humans can and should only submit. But Malthus's 'iron law' is empirically flawed, since we know from history that technological and social innovation can discover and produce new resources, from methods of producing light (from oil lamps to candles to LEDs) to the 1970s green revolution in agriculture. There isn't much natural about 'natural resources': they are all produced by the combination of human knowledge, innovation, and labour, and their particular natural inputs are only contingent. But even if resources are constrained, why is saving them the only ethical concern, rather than using them efficiently (not wastefully) for valuable projects? Surely the point of resources is their instrumental value - what they can do for us. So what are we saving those resources for, if every future generation will also follow the same ethical argument and save them for their future generations?
Secondly, what about the rights and interests of the other people we share this world with right now? Shouldn't we be concerned with the rights of present generations as well as the rights of future generations? Sustainability as maximising future resources allows us to criticise the status quo because too many resources are being used up (in the aggregate), but it says nothing about the current distribution of that resource consumption, implicitly going along with its present great global inequality.
III. Meeting the Needs of All
In contrast, Gro Brundtland's influential 1987 report On Our Common Future links environmental, intergenerational, and distributive concerns. Her famous definition of sustainable development is "development that meets the needs of the present without compromising the ability of future generations to meet their own needs" where 'needs' means overriding priority for the essential needs of the world's poor, under limitations that are not absolute but are imposed by the state of technology and social organization on the environment's resources and ability to absorb the effects of human activities. Brundtland was optimistic that economic growth that met those requirements could achieve a more prosperous, just and secure future.
This is a much better, more ethically sophisticated definition of sustainability. It doesn't fetishise the environment, but incorporates it as instrumentally relevant into a just, feasible and human well-being centred view of progress. The only criticism would be that Brundtland's concept of the person is not ambitious enough: essential needs are not the only things people have reason to care about and use resources for, so restricting our concerns for sustainable development merely to sustaining needs is not enough.
IV. Preserving and Expanding Freedoms
And so to our final idea of sustainability. In The Idea of Justice Amartya Sen argues that we should be much more ambitious about expanding our idea of basic needs as we get richer (development means raising our standards as well as meeting them), but he also emphasises the importance of the agency of individuals - of freedoms - over and above our basic physiological needs. Sen's 'agency perspective' includes for example that:
i) people can have reasons for conservation that are non-instrumental to meeting basic needs, whether aesthetic or otherwise (this re-incorporates the possibility of 'do no harm' as one goal for human activity among others);
ii) there is a value to participatory public discussion about what sustainable development entails, even if some technocratic policy analysis is more efficient (if a society is going to decide to value the non-instrumental value of rare and beautiful species and ecosystems for example, perhaps at the cost of economic growth, this should be a public decision);
iii) people may want to distinguish and particularly protect certain opportunities apart from their aggregate well-being impact e.g. even if our grandchildren are much richer than us and can live for 200 years, we might still like them to be able to breathe fresh air outdoors (i.e. justice for future generations is more than securing their general purpose wealth - we may want to secure them particular things that we particularly cherish);
iv) it is important to consider not only aggregate well-being and specific opportunities, but also how they are accomplished (e.g. procedural constraints on policies like population control that fail to sustain our freedoms right now).
Sen therefore proposes what seems to me the best definition of sustainability so far:
the preservation, and when possible expansion, of the substantive freedoms and capabilities of people today without compromising the capability of future generations to have similar - or more - freedom.
This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License. Attribution: Thomas R. Wells is a philosopher at