This past weekend, the philosophy department here at the University of Calgary hosted a conference on Sustainability with a focus on intergenerational justice. A topic of much debate was what exactly should be sustained/left for future generations. Now, I am very much an outsider to this debate, but one candidate of a necessary (but insufficient) component of the class of things to be sustained has occurred to me, and I would be interested to find out whether this seems reasonable or workable to theorists working in this area.
The underlying assumption is that there are certain biological and/or biochemical processes that are necessary for the continuation of human life. (I am going to talk about human life, but I think this will generalize.) It is then plausible to assume that these processes can, at least in principle, be described by formalised sentences in the language of biology or something similar. My suggestion then, is that at the bare minimum what needs to be sustained is a collection that satisfies the Ramsification of the sentences describing the basic life sustaining processes.
To Ramsify a sentence of a formal language is to replace all non-logical terms, which is to say names of things, with free variables of the appropriate type, and then binding those variables with existential quantifiers. The idea is, in this case, roughly that we want to require that certain functional roles are filled without specifying exactly what is filling those roles.
Take the example of water. Water plays certain functional roles in sustaining human life, but consider a future in which people have figured out how to synthesize a substance, schmater (presumably composed of molecules of XYZ), which plays exactly the same functional roles as water. What we want to maintain for future generations is sufficient water OR schmater. My requirement captures this is generality by requiring only that there always be something that plays a particular functional role in the maintenance of human life.
Note that I have said ‘always’. Thus the collection of things satisfying a particular Ramsey-sentence must exist at any time at which the relevant process occurs. So, for example, the magnitude of the temporal gap between there not being enough water, and there being enough schmater (or water plus schmater) must be near zero.
This idea obviously needs more refinement, and is certainly not sufficient for the maintenance of human life, but it seems to me that it tracks one component of sustainability better than trying to specify exactly which resources need be maintained.