Friedman did not just demonstrate that monetary policy plays a vital role in broader economic stability. He also argued that economists got their monetary policy wrong in the 1950s and 1960s by misunderstanding the relationship between inflation and unemployment. In Friedman's view, previous generations of economists had no justification for believing that governments could permanently decrease unemployment by allowing inflation - and vice versa.

Its arguments would go on to shape global economics and influence world leaders in the late 20th century, but Capitalism and Freedom was largely ignored when it was first published in 1962. The first work written for the general public by American economist Milton Friedman, the book argues that a free market with little government interference is the best way to run society.

In his best-selling 2013 book, Capital in the Twenty-First Century, Piketty takes issue with the idea that, despite the odd bump along the way (not least the 2007-08 global financial crisis), inequality tends to decline as capitalism matures. Piketty spent 15 years building an unparalleled database on wealth and income in France, the United States, and a number of other countries. He uses this data to argue that the opposite is true. Capitalism's natural tendency is, he says, to move toward ever-greater inequality.

More than 200 years after Adam Smith published The Wealth of Nations, governments around the world continue to address many of the issues discussed in the book. The most powerful states in the world are still committed to international trade, but questions are repeatedly asked about the role of governments in the economy and the effectiveness of the free market.

Geneva-born thinker Jean-Jacques Rousseau's famous work of political philosophy from 1762 is based on a give-and-take theory of the relation between individual freedom and social order: the social contract that gives the work its name. Rousseau thinks about the issue by starting with what is known as the state of nature, a lawless condition where people are free to do what they like, governed only by their own instinctive sense of justice. People are free, but they are also vulnerable to chaos.

Austrian-born economist Friedrich Hayek's 1944 work, The Road to Serfdom, analyzes the ways in which excessive government planning can erode democracy. Published while World War II still raged, the work draws influential parallels between the totalitarianism of both socialism and Nazism and increasing control exerted by Western democracies.

Western thinking about the Middle and Far East has been distorted by stereotype and inaccuracy. This argument lies at the center of Palestinian-American literary theorist Edward Said's groundbreaking book, Orientalism. Originally published in 1978, it cemented Said's reputation as the father of postcolonial studies.

Why do we want to justify our decisions, even if they appear to be irrational? The answer lies in cognitive dissonance, the mental discomfort we experience when we hold two contradictory beliefs at the same time. In A Theory of Cognitive Dissonance, first published in 1957, American social psychologist Leon Festinger investigates the problem. Festinger puts forward the idea that we have developed mechanisms to try to deal with the stress brought on by cognitive dissonance.

In his 1983 book Nations and Nationalism, British-Czech intellectual Ernest Gellner put forward a theory of nationalism, explaining that the concept of nation is not in fact an ancient notion, as we might first imagine. Rather, it is a modern idea born out of the seismic social and cultural shifts that industrialization brought to the Western world.

In his 1996 book The Clash Of Civilizations and the Remaking of World Order, American political scientist Samuel Huntington sets out his vision of the post-Cold War world. While the era from 1945 to 1989 was shaped by ideological conflict (communism vs. capitalism), Huntington predicts a future of cultural conflict.

One of the most influential works of political theory ever written, The Federalist Papers collects 85 essays from 1787 and 1788, when the United States was a new country looking to find its way politically. Thomas Jefferson, author of the country's Declaration of Independence and a future US president, called the work "the best commentary on the principles of government which ever was written".

William worked on The Principles of Psychology throughout the 1880s, while teaching psychology and philosophy at Harvard University. He drew together various styles of science to create a unified whole, and to establish psychology as a valid discipline. Not only did he achieve this, but he also created concepts - such as thought being a "stream of consciousness" - that have found their way into both the arts, and popular conversation.

Issues of human rights and freedoms always inflame passions, and John Rawls's A Theory of Justice will do the same. Published in 1971, it links the idea of social justice to a basic sense of fairness that recognizes human rights and freedoms. Controversially, though, it also accepts differences in the distribution of goods and services - as long as they benefit the worst off in society.

More than two centuries after its initial publication in 1781, Immanuel Kant's Critique of Pure Reason remains perhaps the most influential text in modern philosophy. Kant himself claimed his work as a revolutionary document and insisted that it changed the discipline of philosophy as thoroughly as Copernicus had changed astronomy 300 years earlier, when he said the Earth revolved around the sun and not the other way round.

First published in 1651, Leviathan drove important discussions about where kings get their authority to rule and what those kings must, in turn, do for their people. This is known as the "social contract". Thomas Hobbes wrote the book while exiled from his native England following the English Civil War that unseated King Charles I. In the face of England's radical - if temporary - rejection of its monarchy, Hobbes wanted to explain why it was important to have a strong central government, which in his time meant having a sovereign at its head.