 John Stuart Mill (1806–1873), in chapter 17 of Considerations on Representative Government (1861), recommended federations among “portions of mankind” not disposed to live under a common government, to prevent wars among themselves and protect against aggression. He would also allow the center sufficient powers so as to ensure all benefits of union—including powers to prevent frontier duties to facilitate commerce. He listed three necessary conditions for a federation: sufficient mutual sympathy “of race, language, religion, and, above all, of political institutions, as conducing most to a feeling of identity of political interest”; no member unit so powerful as to not require union for defense nor tempt unduly to secession; and rough equality of strength among member units to prevent internal domination by one or two. Mill also claimed among the benefits of federations that they reduce the number of weak states hence reduce temptation to aggression, ending wars and restrictions on commence among member units; and that federations are less aggressive, only using their power defensively. Further benefits from federations—and from decentralized authority in general—might include learning from ‘experiments in living’.