Discourse on the Origin and Basis of Inequality Among Men by the philosopher Jean-Jacques Rousseau was originally written for an essay competition run by the Dijon Academy of Arts and Sciences in 1754. The question was, "What is the origin of inequality among men, and is it authorized by the natural law?" Rousseau's text is divided into four main parts: a dedication, preface, an extended inquiry into the nature of the individual, and another inquiry into the evolution of the human species within society.

John Locke and his works - particularly An Essay Concerning Human Understanding - are regularly and rightly presented as foundations for the Age of Enlightenment. His primary epistemological message - that the mind at birth is a blank sheet waiting to be filled by the experiences of the senses - complemented his primary political message: that human beings are free and equal and have the right to envision, create and direct the governments that rule them and the societies within which they live.

The Reveries of the Solitary Walker was one of the last works written by the French philosopher Jean-Jacques Rousseau (1712-1778) and was, in fact, not quite complete. It was published four years after his death and came quickly to be regarded as one of his most poetic works. It consists of 10 Walks (only the final ‘Walk’ was unfinished) during which he muses on a variety of topics including thoughts on issues which featured strongly in his notable life as a philosopher and commentator, including education and political philosophy.

Though Karl Marx is best known for Capital and The Communist Manifesto, his revolutionary thoughts and ideas had developed over decades spent in study, discussion and association with a variety of organisations throughout Europe and the US, intent on challenging the establishment order. These six very different texts show how Marx’s ideas evolved and how increasingly fierce his views became.

Man is born free, and everywhere he is in chains. In The Social Contract, Rousseau explores the concept of freedom and the political structures that may enable people to acquire it. He argues that the sovereign power of a state lies not in any one ruler but in the will of the general population. Rousseau argues that the ideal state would be a direct democracy where executive decision making is carried out by citizens who meet in assembly, as they would in the ancient city-state of Athens.

Though Twilight of the Idols (written in a week in 1888 and subtitled How to Philosophise with a Hammer) came near the end of Nietzsche’s creative life, he actually recommended it as a starting point for the study of his work. This was because from the beginning he viewed it as an introduction to his wide-ranging views.

Aristotle's Metaphysics was the first major study of the subject of metaphysics - in other words, an inquiry into 'first philosophy', or 'wisdom'. It differs from Physics which is concerned with the natural world: things which are subject to the laws of nature, things that move and change, are measurable. In Metaphysics, the study falls on 'being qua being' - being insofar as it is being; the causes and principles of being, the causes and principles of substances.

Immanuel Kant’s Critique of Pure Reason can lay claim to being the most important single work of modern philosophy, a work whose methodology, if not necessarily always its conclusions, has had a profound influence on almost all subsequent philosophical discourse. In this work Kant addresses, in a groundbreaking elucidation of the nature of reason, the age-old question of philosophy: “How do we know what we know?” and the limits of what it is that we can know with certainty.

In the 21st century, Carl Gustav Jung (1875-1961) remains one of the key figures in the field of analytical psychology - and Psychological Types, or The Psychology of Individuation, published in 1921, is one of his most influential works. It was written during the decade after the publication of Psychology of the Unconscious (1912), which effectively ended his friendship and collaboration with Sigmund Freud.

Sigmund Freud (1856-1939) is remembered as the father of psychoanalysis. Civilization and Its Discontents (1930) is one of his key works, written three decades after his seminal book The Interpretation of Dreams. In it he considers the conflict between the needs of the individual acting both egotistically and altruistically in the pursuit of happiness and the myriad demands of civilised society and the ensuing tensions this clash of needs and demands generates.