In 1929, Martin Heidegger (1889-1976) published his remarkable book Kant and the Problem of Metaphysics. The Kantbuch, as Heidegger often called it, is regarded by many as a vital supplement to the unfinished second part of Heidegger’s most influential work, Being and Time, which was published two years earlier in 1927.

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.

Philosophical Investigations was published in 1953, two years after the death of its author. In the preface written in Cambridge in 1945 where he was professor of philosophy he states: ‘Four years ago I had occasion to re-read my first book (the Tractatus Logico-Philosophicus) and to explain its ideas to someone. It suddenly seemed to me that I should publish those old thoughts and the new ones together: that the latter could be seen in the right light only by contrast with and against the background of my old way of thinking.’

As philosophy professor Taylor Carman explains in his helpful introduction, Edmund Husserl (1859-1938) was the founder of modern phenomenology, one of the most important and influential movements of the 20th century. Ideas, published in 1913 – its full title is Ideas for a Pure Phenomenology and Phenomenological Philosophy – was the key work. It is arguably ‘the most fundamental and comprehensive statement of the fundamental principles of Husserl’s mature philosophy’.

Philosophy of Mind is the third and final part of the Encyclopaedia of the Philosophical Sciences, the collection in which Hegel (1730-1831) offered an overview of his life’s work. Though originally written in 1817, he revised it in 1830, thus providing a finished form the year before his death. Hegel used the three parts of the Encyclopaedia - Science of Logic, Philosophy of Nature and Philosophy of Mind - as a basis for lectures at the Universities of Heidelberg which he joined in 1816, and in Berlin in 1820.

Benedict de Spinoza's Ethics, first published in 1677, constitutes a major systematic critique of the traditional and religious foundations of philosophical thought. In it, Spinoza follows a logical step-by-step format consisting of definitions, axioms, propositions, proofs, and corollaries to create a comprehensive inquiry into the truth about God, nature, and humans' place within the universe. From these broad metaphysical themes, Spinoza derives what he considered to be the highest principles of religion and society and lays out an ethical system in which reason is the supreme value.

This Leibniz collection contains some of the philosopher’s most important works and ideas, spans three decades and illuminates the fascinating intellectual journey undertaken by him in his quest for truth. A prodigious polymath, Leibniz was a mathematician, philosopher, physicist and statesman and engaged with a sweeping range of ideas and disciplines, striving throughout his life to be at the cutting edge of scientific thinking. These Principal Essays are arranged in chronological order.

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.

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.

Two contrasting reflections by Aristotle which cover very particular ground. In 'On the Soul', Aristotle presents his view of the 'life essence' which, he argues, is possessed by living things whether plants, animals or humans. Not a 'soul' in the generally accepted Western use of the term, this 'soul', he says, is a life force that is indivisible from the organism that possesses it.

Matter and Memory, (Matière et Mémoire), published in 1896, was the second book written by Henri Bergson (1859-1941), one of the leading French philosophers of his age. It followed Time and Free Will (1889) and helped to establish him as a major force in anti-mechanistic thought, opposing the trend towards uncompromisingly secular and scientific views. However, when Matter and Memory appeared, Bergson was 39 and had yet to become the hugely influential figure he became in the first decades of the 20th century.

Martin Heidegger, considered by some to be the greatest charlatan ever to claim the title of "philosopher", by some as an apologist for Nazism, and by others as an acknowledged leader in continental philosophy, is probably the most divisive thinker of the 20th century. In the second edition of this Very Short Introduction audiobook, Michael Inwood focuses on Heidegger's most important work, Being and Time, to explore its major themes of existence in the world, inauthenticity, guilt, destiny, truth, and the nature of time.

The Tractatus Logico-Philosophicus (Logical Philosophical Treatise or Treatise on Logic and Philosophy) is the only full-length philosophical book by the Austrian philosopher Ludwig Wittgenstein that was published during his lifetime. The goal of the work is to identify the relationship between language and reality and to define the limits of science. He famously summarized the book in the following way: "What can be said at all can be said clearly; and what we cannot talk about we must pass over in silence."

Henri Bergson (1859-1941) was the leading French philosopher of the first half of the 20th century. Near the end of his life when he was forced to register with the police in Nazi occupied France he wrote: ‘Academic. Philosopher. Nobel prize winner. Jew.’ Time and Free Will, his doctoral thesis, was published as a book in 1889 and attacks and rejects the mechanistic view of causality described in Kant’s version of space and time and proceeds to attempt to define free-will and consciousness by separating space and time.

This first new translation of Kierkegaard's masterwork in a generation brings an essential work of modern philosophy to vivid life. While the majority of Kierkegaard's work leading up to The Concept of Anxiety dealt with the intersection of faith and knowledge, here the renowned Danish philosopher turns to the perennial question of sin and guilt. First published in 1844, this concise treatise identified - long before Freud - anxiety as a deep-seated human state, one that embodies the endless struggle with our own spiritual identities.

In 1929, Martin Heidegger (1889-1976) published his remarkable book Kant and the Problem of Metaphysics. The Kantbuch, as Heidegger often called it, is regarded by many as a vital supplement to the unfinished second part of Heidegger’s most influential work, Being and Time, which was published two years earlier in 1927.

As philosophy professor Taylor Carman explains in his helpful introduction, Edmund Husserl (1859-1938) was the founder of modern phenomenology, one of the most important and influential movements of the 20th century. Ideas, published in 1913 – its full title is Ideas for a Pure Phenomenology and Phenomenological Philosophy – was the key work. It is arguably ‘the most fundamental and comprehensive statement of the fundamental principles of Husserl’s mature philosophy’.

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.

Critique of Judgement was published in 1790 and is divided into two parts, the Critique of Aesthetic Judgement and the Critique of Teleological Judgement. Our ‘judgements of taste’, as Kant describes our aesthetic judgements, have both a personal and a universal function: personal, because we have a subjective aesthetic response to the ‘agreeable’, the ‘beautiful’, the ‘sublime’ and the ‘good’; but also there is a ‘universal’ aspect because our aesthetic response has a ’disinterested’ element. This brings under Kant’s spotlight, for example, the concept of beauty and the perception of beauty.

Kant's Prolegomena, although a small book, is without doubt the most important of his writings, writes the translator, Paul Carus. Prolegomena means, literally, prefatory or introductory remarks, and it furnishes us with a key to his main work, The Critique of Pure Reason; in fact, it is an extract containing all the salient ideas of Kant's system. It approaches the subject in the simplest and most direct way and is therefore best adapted as an introduction into his philosophy.

The Critique of Practical Reason was published in 1788, seven years after Immanuel Kant's major work, Critique of Pure Reason. In it, Kant sets out his moral philosophy - and it proved a seminal text in the history of the subject. He argues that the summum bonum (the highest good) of life is that rather than just pursuing happiness, people should inhabit a moral dimension that enables them to deserve the happiness that God can give. Though much shorter than Critique of Pure Reason, this is the sourcebook for Kant’s ethical doctrines.

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.

This Leibniz collection contains some of the philosopher’s most important works and ideas, spans three decades and illuminates the fascinating intellectual journey undertaken by him in his quest for truth. A prodigious polymath, Leibniz was a mathematician, philosopher, physicist and statesman and engaged with a sweeping range of ideas and disciplines, striving throughout his life to be at the cutting edge of scientific thinking. These Principal Essays are arranged in chronological order.

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.

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.

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.

Critical theory emerged in the 1920s from the work of the Frankfurt School, the circle of German-Jewish academics who sought to diagnose—and, if at all possible, cure—the ills of society, particularly fascism and capitalism. In this book, Stephen Eric Bronner provides sketches of leading representatives of the critical tradition (such as George Lukács and Ernst Bloch, Theodor Adorno and Walter Benjamin, Herbert Marcuse and Jurgen Habermas) as well as many of its seminal texts and empirical investigations.

Though it first aroused anger and controversy rather than admiration and acceptance, A Theologico-Political Treatise was a landmark in the analysis of theology (with particular reference to the Bible and its Jewish and Christian interpretations) and its relationship to philosophy and politics. Spinoza’s scholarly analysis, based on careful study, demonstrated that the Bible was composed by many writers over the centuries - and that even the Pentateuch, the first five books, were not the work of Moses, as was generally assumed at the time.

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.

The Wealth of Nations, first published in 1776, is the first book of modern political economy and still provides the foundation for the study of that discipline. Along with important discussions of economics and political theory, Smith mixed plain common sense with large measures of history, philosophy, psychology, sociology and much else. Few texts remind us so clearly that the Enlightenment was very much a lived experience, a concern with improving them human condition in practical ways for real people.