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close friend Heinrich Köselitz and his sister Elizabeth Förster-Nietzsche to go through the remaining notebooks and unpublished writings, choosing sections of particular interest to produce The Will to Power, giving it the subtitle An Attempted Transvaluation of All Values.

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....

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.'

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'.

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.

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.

'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.

Man and His Symbols owes its existence to one of Jung's own dreams. The great psychologist dreamed that his work was understood by a wide public, rather than just by psychiatrists, and therefore he agreed to write and edit this fascinating book. Here, Jung examines the full world of the unconscious, whose language he believed to be the symbols constantly revealed in dreams.

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.  

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.

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".

Jung's discovery of the 'collective unconscious', a psychic inheritance common to all humankind, transformed the understanding of the self and the way we interpret the world. In On the Nature of the Psyche Jung describes this remarkable theory in his own words, and presents a masterly overview of his theories of the unconscious, and its relation to the conscious mind. Also contained in this collection is On Psychic Energy, where Jung defends his interpretation of the libido, a key factor in the breakdown of his relations with Freud. 

Aristotle’s Organon comprises six key essays on logic, initially collected by Theophrastus, his successor as head of the Peripatetic school, and given its final form by Andronicus some three centuries later. The six essays are: Categories, On Interpretation, Prior Analytics, Posterior Analytics, Topics and On Sophistical Refutations. One of the principal topics of Aristotle’s focus is syllogism, in which two premises (one major, one minor) lead to a conclusion. This features in Prior Analytics and On Interpretation.

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.