 Lastly, our knowledge of the future is limited. While we can know the particular identities of presently existing people (and very many previously living people), we are normally not in a position to refer to specifically identifiable future persons. It is not that all predictions about the future decrease in certainty at some constant rate (see Cowen &amp; Parfit 1992: 148). Indeed, many predictions are more likely to be true concerning the further future than the more immediate future. For example, the prediction that some policy will have changed or that certain resources will have been exhausted is more likely to be true in the further future. Nonetheless, we cannot know the specific identities of persons in the further future. Our lack of certain knowledge of the future also means that we often will be in a position to know at best merely the likelihood of normatively relevant consequences of alternative long-term policies.