Ever since Montesquieu's 'The Spirit of the Laws' (1748), the principle of the separation of powers has come to dominate important themes of government, particularly related to the institutional division and diffusion of power for the purposes of limiting and prevention despotism and, more recently, corruption. But was this vision truly limited to only three species of power (legislative, executive and judicial)? Do international constitutional trends towards the entrenchment of independent integrity institutions (anti-corruption agencies, auditors-general, ombudsmen and the like) indicate a fundamental and lasting evolution toward a more sophisticated framework, requiring a rethinking of how horizontal and vertical accountability interrelate in modern society? This national presidential address and its accompanying commentaries will review current Australian debates and international evidence over whether such an evolution is occurring, how it should be understood, whether it should be valued and how it can be reconciled with existing constitutional traditions.