There is a cause, or a reason, behind everything that happens. This is the fundamental view behind the classical proposition the Principle of Sufficient Reason, which, in 1813, Schopenhauer chose as his subject for further examination in his doctoral dissertation On the Fourfold Root of the Principle of Sufficient Reason....

It was with Human, All Too Human, first published in 1878, that Nietzsche developed the aphoristic style that so suited his challenging views and uncompromising style. The text is divided into three main sections: 'Of the First and Last Things', 'History of the Moral Feelings' and 'The Religious Life'.

The essays in The Two Fundamental Problems of Ethics have a rather special place in Schopenhauer’s work, both being written as entries to Scandinavian philosophy competitions, one in Norway and one in Sweden.

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.

Continuing where Thus Spoke Zarathustra left off, Nietzsche's controversial work Beyond Good and Evil is one of the most influential philosophical texts of the 19th century and one of the most controversial works of ideology ever written. Attacking the notion of morality as nothing more than institutionalised weakness, Nietzsche criticises past philosophers for their unquestioning acceptance of moral precepts. Nietzsche tried to formulate what he called "the philosophy of the future".

'The two foes of human happiness are pain and boredom.' Arthur Schopenhauer (1788-1860) was one of the most influential philosophers of the 19th century because his humanistic, atheistic, if pessimistic views chimed with a new secularism that was emerging from a Western society dominated by religion. Despite his rather forbidding image (and a few outdated views), he is one of the most approachable German philosophers, and this is certainly evident in these two key works, The Wisdom of Life and Counsels and Maxims.

Perhaps one of the most revolutionary works of philosophy ever presented, The Phenomenology of Spirit is Hegel's 1807 work that is in numerous ways extraordinary. A myriad of topics are discussed, and explained in such a harmoniously complex way that the method has been termed Hegelian dialectic. Ultimately, the work as a whole is a remarkable study of the mind's growth from its direct awareness to scientific philosophy, proving to be a difficult yet highly influential and enduring work.

Nietzsche never recovered from his mental breakdown in 1889 and therefore was unable to further any plans he had for the ‘magnum opus’ he had once intended, bringing together in a coherent whole his mature philosophy. It was left to his close friend Heinrich Köselitz and his sister Elizabeth Förster-Nietzsche to go through the remaining notebooks and unpublished writings, choosing sections of particular interest to produce The Will to Power, giving it the subtitle An Attempted Transvaluation of All Values.

Composed in four parts between 1883 and 1885, Thus Spoke Zarathustra is the most famous and influential work of German philosopher Friedrich Nietzsche. The work is a philosophical novel in which the character of Zarathustra, a religious prophet-like figure, delivers a series of lessons and sermons in a Biblical style that articulate the central ideas of Nietzsche's mature thought.

In On the Genealogy of Morals, subtitled "A Polemic", Nietzsche furthers his pursuit of a clarity that is less tainted by imposed prejudices. He looks at the way attitudes towards 'morality' evolved and the way congenital ideas of morality were heavily colored by the Judaic and Christian traditions.

Being and Time was published in 1927 during the Weimar period in Germany, a time of political, social and economic turmoil. Heidegger himself did not escape the pressures and his nationalism, and undeniable anti-Semitism in the following decades cast a shadow over the man, but not the work. Being and Time is not coloured by expressions of his later views (unlike other writings) and remains an outstanding document.

Durant lucidly describes the philosophical systems of such world-famous “monarchs of the mind” as Plato, Aristotle, Francis Bacon, Spinoza, Kant, Voltaire, and Nietzsche. Along with their ideas, he offers their flesh-and-blood biographies, placing their thoughts within their own time and place and elucidating their influence on our modern intellectual heritage. This book is packed with wisdom and wit.

One of the most popular and beloved introductions to the concept of faith ever written, Mere Christianity has sold millions of copies worldwide. This audiobook brings together C. S. Lewis' legendary radio broadcasts during the war years, in which he set out simply to "explain and defend the belief that has been common to nearly all Christians at all times."

First published in 1930, Civilization and Its Discontents is one of the most influential works of pioneering psychologist Sigmund Freud. Focusing on the tension between the primitive drives of the individual and the demands of civilization for order and conformity, Freud draws upon his psychoanalytic theories to explain the fundamental structures, conflicts, and consequences of society.

The Gay Science (The Joyful Wisdom) is one of Nietzsche's greatest books. His wonderfully fertile mind roams over mankind, his thoughts, his emotions, his behaviour and his weaknesses with remarkable clarity, with insight - but also with humour!In this work are 383 separate paragraphs, some short, some long, but all singular observations - the epitome of his famous aphoristic style. 'Morality is the herd instinct in the individual.'