as done above and of making the preceding remarks is to establish a context in which the important policy issues can be formalized explicitly.
The conservation criterion, or at least, its more ordinary manifestation as a sustainable yield criterion, is often criticized on the grounds that it does not maximize the present value of the yield's benefits. This reasoning is surely wrong. It is no more appropriate to conclude that the sustainable yield criterion is invalid because it does not satisfy the present value criterion than it is appropriate to conclude that the present value criterion is invalid because it does not satisfy the sustainable yield criterion. One cannot use one criterion to bludgeon another. They are on the same logical level. The most one can say at this point is that the two criteria conflict; they imply different states of the world.
One can judge a criterion, however, by its implications and by the conditions under which it leads to desirable consequences. We have seen that it is possible to view the natural resource sector much as a single productive asset, even including "nonrenewable" virgin materials. No criterion emerges as clearly superior to all others. But it is clear that there is a world of difference between the statements, "The earth belongs to the living" and "The earth belongs in usufruct to the living."