Maslow's 1943 essay established his idea of humanistic psychology as a "third force" in the field. While psychoanalysts sought to understand behaviour by uncovering subconscious desires and behaviourists through analysis of conditioned behaviours.

200 years after it was written, Adam Smith published The Wealth of Nations is still debated by governments internationally. Smith argued that 'mercantilism'-the theory that the national economy exists solely to strengthen the government, thus the government should regulate the economy-was wrong.

In the 1960s, researchers began to understand memory as operating under two systems: a short-term one handling information for mere seconds, and a long-term one for managing information indefinitely. Short-term memory, they found, wasn't simply a 'filing cabinet,' but appeared to work on cognitive tasks.

Alasdair MacIntyre's 1981 After Virtue was a ground-breaking contribution to modern moral philosophy. Dissatisfied with the major trends in the moral philosophy of his time, MacIntyre argued that modern moral discourse had no real rational basis.

Much of what we now know about the influence of early childhood environments on delinquency and anti-social behavior can be traced to Bandura's ground-breaking 1973 book. He uses the subject of aggression to demonstrate the usefulness of social learning theory.

Albert Hourani's A History of the Arab Peoples is unsurpassed as an overview of Arab history from the rise of Islam to the late twentieth century. Going far beyond political history, it provides a deep analysis of social, cultural and economic structures.

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

Democracy in America, published in 1835 and 1840, challenged conventional thinking about democracy when it first appeared and is still cited today for its in-depth analysis of what makes a successful democracy.