Possible environmental and related impacts of human activity are shown to include the extinction of humanity and other sentient species, excessive human numbers, and a deteriorating quality of life (I). I proceed to argue that neither future rights, nor Kantian respect for future people’s autonomy, nor a contract between the generations supplies a plausible basis of obligations with regard to future generations. Obligations concern rather promoting the well-being of the members of future generations, whoever they may be, as well as of current generations. Future benefits and costs should only be discounted where there are special reasons for doing do so (e.g. relevant opportunity costs) (II). A sustainable economy is held to be necessary for intergenerational equity. This granted, principles of equity are introduced concerning: compensation for long-term risks and for resource depletion; conserving the stock of resources, resource diversity, and assimilative capacity; equal options and opportunities for each generation; and remedying past failures to conserve environmental quality. Rules and policies considered include: an efficient, diversified, and ecologically sustainable economy; no increase of risk of irreversible environmental change; and action despite uncertainty to avert serious future outcomes (the Precautionary Principle). These policies are argued to require rectification of current injustices within and between current generations (III). Finally, the recently resuscitated metaphysical model of society as a partnership between generations is held to imply the view of each generation as trustees rather than owners of the planet. This trusteeship view is independently credible, and supportive of the principles and policies earlier introduced; and its adoption by successive generations could turn the partnership model into a reality (IV).
