Liberty is hardly the "natural" order of things. In most places and at most times, the strong have dominated the weak and human freedom has been quashed by force or by customs and norms. Either states have been too weak to protect individuals from these threats or states have been too strong for people to protect themselves from despotism. Liberty emerges only when a delicate and precarious balance is struck between state and society.

There is a happy Western myth that political liberty is a durable construct, a steady state, arrived at by a process of "enlightenment." This static view is a fantasy, the authors argue; rather, the space to attain and maintain liberty stays open only via a fundamental and incessant struggle between state and society. The power of state institutions and the elites that control them has never gone uncontested in a free society. In fact, the capacity to contest them is the definition of liberty. State institutions have to evolve continuously as the nature of conflicts and needs of the society change, and thus society's ability to keep state and rulers accountable must intensify in tandem with the capabilities of the state. This struggle between state and society becomes self-reinforcing, inducing both to develop a richer array of capacities just to keep moving forward along the corridor. Yet this struggle also underscores the fragile nature of liberty. It is built on a delicate balance between state and society, between economic, political and social elites and citizens, between institutions and norms. One side of the balance gets too strong, and as it has often happened in history, liberty begins to wane. Liberty depends on the vigilant mobilization of society. But it also needs state institutions to continuously reinvent themselves in order to meet new economic and social challenges that can easily close the space liberty needs to survive.

Today we are in the midst of a time of wrenching destabilization. We need liberty more than ever, and yet the corridor to liberty is getting narrower and more treacherous. The danger on the horizon is not "just" the loss of our political freedom, however grim that is in itself; it is also to the prosperity and safety that critically depend on liberty. The opposite of the corridor of liberty is the road to ruin.

Daron Acemoglu is the Elizabeth and James Killian Professor of Economics at MIT. In 2005 he received the John Bates Clark Medal, given to economists under age forty judged to have made the most significant contribution to economic thought and knowledge, in 2012 he was awarded the Erwin Plein Nemmers Prize in economics for work of lasting significance, and in 2016 he received the BBVA Frontiers of Knowledge Award in economics, finance, and management for his lifetime contributions.

James A. Robinson, a political scientist and economist, is one of nine University Professors at the University of Chicago. Focused on Latin America and Africa, he is currently conducting research in Bolivia, the Democratic Republic of the Congo, Sierra Leone, Haiti, and Colombia, where he has taught for many years during the summer at the University of the Andes in Bogotá.