 Nash (1950) adopted a welfarist framework, in which alternatives are described only by the utility levels they give to the two parties. His solution consists in choosing the alternative which, in the feasible set, maximizes the product of individual utility gains from the disagreement point (this point is the fallback option when the parties fail to reach an agreement). This solution is therefore related to a particular social welfare function which is somehow intermediate between sum-utilitarianism and the maximin criterion. Contrary to these, however, it is invariant to independent changes in utility zeros and scales, which means that it can be applied with utility functions which are defined only up to an affine transformation (i.e., no difference is made between utility function Ui and utility function ai Ui + bi), such as Von Neumann-Morgenstern utility functions. Nash uses this invariance property in his axiomatic characterization of the solution. He also uses another property, which holds for any solution maximizing a social welfare function, namely, that removing non-selected options does not alter the choice.