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his close friend Heinrich Köselitz and his sister Elizabeth Förster-Nietzsche to go through the remaining notebooks and unpublished writings, choosing sections of particular interest to produce The Will to Power, giving it the subtitle An Attempted Transvaluation of All Values.

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".

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 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.'

Nietzsche was one of the most revolutionary thinkers in Western philosophy and Thus Spoke Zarathustra remains his most influential work. It describes how the ancient Persian prophet Zarathustra descends from his solitude in the mountains to tell the world that God is dead and that the Superman, the human embodiment of divinity, is his successor. With blazing intensity, Nietzsche argues that the meaning of existence is not to be found in religious pieties or meek submission, but in an all-powerful life force: passionate, chaotic and free.

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.

From the perspective of an unbeliever, Fear and Trembling explores the paradox of faith, the nature of Christianity, and the complexity of human emotion. Kierkegaard examines the biblical story of Abraham, who was instructed to sacrifice his son Isaac, and forces us to consider Abraham's state of mind. What drove Abraham, and what made him carry out such an absurd and extreme request from God? Kierkegaard argues that Abraham's agreement to sacrifice Isaac, and his suspension of reason, elevated him to the highest level of faith.

Schopenhauer was just 30 when his magnum opus, Die Welt als Wille und Vorstellung, a work of considerable learning and innovation of thought, first appeared in 1818.

Much to his chagrin and puzzlement (so convinced was he of its merits), it didn't have an immediate effect on European philosophy, views and culture. It was only decades later that it was recognised as one of the major intellectual landmarks of the 19th century.

Friedrich Nietzsche (1844-1900) is one of the towering intellectual figures of the 19th century, a philologist, philosopher and poet of profound complexity and range whose writings in moral philosophy continue to resonate in the present day. The Dawn of Day (Morgenröte), first published in 1881, marked a clear shift in his thinking and prefigures many of the ideas that would be further developed in his later writings. The clue is in the title, sometimes translated as Dawn or Morning, which suggests the beginning of a different awareness.

Thus Spoke Zarathustra is one of the most extraordinary - and important - texts in Western philosophy. It was written by Friedrich Nietzsche between 1883 and 1885. He cast it in the form of a novel in the hope that his urgent message of the 'death of God' and the rise of the superman (Ubermensch) would have greater emotional as well as intellectual impact.

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.

The Red Book, published to wide acclaim in 2009, contains the nucleus of C. G. Jung's later works. It was here that he developed his principal theories of the archetypes, the collective unconscious, and the process of individuation that would transform psychotherapy from treatment of the sick into a means for the higher development of the personality.

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.

Published first in 1912, Psychology of the Unconscious was one of the most important stepping stones in the development of Jung’s thought and practice. It has a long subtitle: A Study of the Transformations and Symbolisms of the Libido. A Contribution to the History of the Evolution of Thought. This expressed the underlying impetus - a break from the view of the libido and its functions as taught by Sigmund Freud, which Jung had earlier adopted. It was from this point that the two approaches, which came to be known as the Swiss and Viennese schools, emerged.

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.