 Let us briefly describe some of the insights that are gained through this theory and seem relevant to political philosophy. A very important one is that there is a conflict between no-envy and solidarity (Moulin and Thomson 1988, 1997). This conflict is well illustrated by the fact that in a market economy, typically any change in technology benefits some agents and hurts others, even when the change is a pure progress which could benefit all. Solidarity principles are not obeyed by allocation rules which pass the no-envy test, and these principles point toward a different kind of distribution, named “egalitarian-equivalence” by Pazner and Schmeidler (1978). An allocation is egalitarian-equivalent when everyone is indifferent between his bundle in this allocation and the bundle he would have in an egalitarian economy defined in some simple way. For instance, the egalitarian economy may be such that everyone has the same bundle. In this case, an egalitarian-equivalent allocation is such that everyone is indifferent between his bundle and one particular bundle. In more sophisticated versions, the egalitarian economy is such that everyone has the same budget set, in some particular family of budget sets. Egalitarian-equivalence is a serious alternative to no-envy for the definition of equality of resources, and its superiority in terms of solidarity is quite significant, in relation to the next point.