sustainable, adj.There are two problems with burning fossil fuels. The first problem is that fossil fuels are running out; the second is that fossil fuels are not running out. The first problem is often called 'peak oil' and the second is known as 'climate change'. If either the first problem or the second is accurate, then we can say that burning fossil fuels is 'not sustainable'. This amounts to arguing that if either A or not-A is true, burning fossil fuels is unsustainable. It seems to be that we can determine sustainability from pure logic. But to get such important results from a tautology, appears to be suspicious at the very least.
4. Ecol. Of, relating to, or designating forms of human economic activity and culture that do not lead to environmental degradation, esp. avoiding the long-term depletion of natural resources.
(Oxford English Dictionary)
Perhaps the problem with our line of reasoning is that we have failed to distinguish between positive and negative effects of an activity. A natural resource running out would not be problem if the use of the resource only imposed costs on society; nor would inexhaustibility be a problem when an activity only provides benefits. So we can rephrase our criterion. If an activity provides benefits and the capability to continue the activity is limited, or if the activity imposes costs and the capability to continue it is not limited, then the activity is not sustainable. From this it can be shown by simple logic that any activity that has both positive and negative effects is not sustainable.
Well at best it seems that sustainability is a pretty hard thing to achieve; and at worst the whole concept looks a little incoherent. Sustainability is, however, an idea to which we often are encouraged to pay homage, despite (or perhaps because of) these problems of definition and coherence.
I think the widespread use of this notion of sustainability explains quite a lot of the religious claptrap surrounding environmental issues. When I say 'religious'; what I mean, broadly, is the tendency of some environmentalists to think about environmental issues in somewhat 'moralistic' terms - 'wind turbines are good', 'cooling towers bad' etc. But such black and white terms may be misleading. The primary concept of value here, "sustainability", is one that, strictly speaking, almost no activities satisfy. This leads, inevitably to a sense of guilt at having to engage in so many activities that seem immoral, and the psychological need for at least some redeeming activities that can make us feel virtuous again. When some such positive activities turn up, there is a great temptation to cover up any negative features (remember any activity with both negative and positive features is unsustainable), even if such downsides actually do exist. So wind turbines may be lovely despite them having some quite serious downsides both in terms of the opinions of those nearby and the reliability of the output they produce. For others nuclear power stations are lovely and wind turbines unlovely. Such distinctions, unless they can be justified by some more fundamental principle, appear somewhat arbitrary.
As an aside, actions with purely negative consequences could be included as 'sustainable' too, if they are exhausted quickly. Perhaps one example is the extra expense in buying a more expensive product (say shampoo) which differs from the standard one by the eco-friendly blurb on the side (say the shampoo is kind to hedgehogs for example). Presumably, your wallet is finite and so limits the damage that your efforts to do the right thing can do.
Some activities fail to be sustainable on both levels. Presumably they both have positive effects and are limited and negative effects and are unlimited. How bad can you get? It's in these cases that the concept of sustainability appear to have serious self-consistency problems. To assert A and not-A is inconsistent; to assert A and B at the same time as not-A and not-B is doubly so. Either fossil fuels are running out or they are not. What should we do? Are wind turbines actually sustainable? What about burning fossil fuels?
A related problem with the categorical notion of sustainability is to do with the idea of criticality. Put bluntly, some aspects of sustainability matter more than others. If my sofa is on fire, then this constitutes a sustainability issue to living in a house. Imagine too that my wooden walls are, over decades, rotting, due to damp and occasional flooding. If I use a fire extinguisher it may well be an unsustainable act, because it causes flooding in the house, and makes my rotting problem worse. But if I don't put out my fire, my house would burn to the ground anyhow. Some may argue that I should instead use a sustainable method to put out the fire; such as finding a blanket in my loft. Rather than use the 'unsustainable' fire-extinguisher; I should use the 'sustainable' fire blanket in my loft. But what if the problem has grown so big by the time I get my fire blanket that the fire is then unmanageable? Failure to focus on our critical problems may lead to undesirable outcomes.
I therefore propose that rather as looking at sustainability as some sort of idol in which we invest all of our scarce hopes, we recognize that all of the activities of humanity are unsustainable. We need to be more precise about things. Instead we need to focus on critical unsustainability of activities that are akin to our house burning down.
I suggest two principles: first, an overall civilization-focus on tackling critical issues and risks, particularly climate change; Secondly the principle that we should do activities only if they add to overall (natural and human) wealth [n759hv]. The notion of wealth may be as difficult to define operationally as sustainability, since it requires some method of valuation over and above that of the market, when dealing with environmental concerns. But it least may well be internally consistent and able to sanely direct those with inflammable furniture.