Treating future people impartially implies avoiding future lives with low well-being

Résumé En

It has been claimed that climate policies can be evaluated by the Pareto principle. However, climate policies lead to different identities and different numbers of future people. Even if one assumes that the number of future people is countably infinite independently of policy choice, the problem is that there exists no natural one-to-one correspondence between the components of the compared alternatives. This non-existence means that the components of streams are indexed by natural numbers that do not correspond to particular people, making a case for impartiakity in the sense of Strong anonymity. Strong anonymity is incompatible with Strong Pareto. The paper re-examines this incompatibility and investigates how far sensitivity for the well-being at any one component can be extended without contradicting Strong anonymity. We show that Strong anonymity combined with four rather innocent axioms has two consequences: (i) There can be sensitivity for the well-being at a particular component of the stream if and only if a finite set of people have higher well-beings, and (ii) adding people to the population cannot have positive social value.