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.

A work that had a huge influence on great thinkers including celebrated German philosopher Immanuel Kant, An Enquiry is Hume's examination of how we obtain information and form beliefs. He argues that we mainly gain knowledge through our senses, a theory known as empiricism. But while the impressions from our senses are key to our beliefs about the world, Hume argues that reason and facts play only a limited part.

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.

Sociologist Émile Durkheim's 1897 work On Suicide is a powerful evidence-based study of why people take their own lives. In the late 19th century it was generally accepted that each suicide was an individual phenomenon, caused by such personal factors as grief, loss, and financial problems. But Durkheim felt there were patterns in suicide rates, and believed that a more likely cause of suicide lay in the individual's relationship to society.

Defining liberty as freedom from interference by state power or popular moral opinion, Mill justifies the individual's right to this liberty by focusing on the role self-development plays in human well-being. His vision of individual rights extends to include freedom of thought and emotion and the freedom to act together with others. Society should protect the development of individuality to aid both social progress and innovation.