In Three Dialogues (set in a ‘Platonic’ garden), Hylas begins by challenging Philonous that he denied the existence of material substance. ‘What!’ says Hylas. ‘Can anything be more fantastical, more repugnant to Common Sense, or a more manifest piece of Scepticism, than to believe there is no such thing as matter?’ And Berkeley, in the guise of Philonous, replies, ‘Softly, good Hylas. What if it should prove that you, who hold there is, are, by virtue of that opinion, a greater sceptic, and maintain more paradoxes and repugnances to common sense, than I who believe no such thing.’

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.

Published in 1748, An Enquiry Concerning Human Understanding is Scottish empiricist philosopher David Hume's distillation of his mature philosophy. Addressing themes including the limits of human understanding, the compatibility of free will with determinism, weaknesses in the foundations of religion, and the appeal of skepticism, An Enquiry Concerning Human Understanding is Hume's attempt to revise and clarify the ideas of his earlier A Treatise of Human Nature.

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.

David Hume (1711-1776) was the most important philosopher ever to write in English as well as a master stylist. This volume contains his major philosophical works. A Treatise of Human Nature (1739–1740), published while Hume was still in his twenties, consists of three books on the understanding, the passions, and morals.

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.

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".

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.

The Theory of Moral Sentiments (1759) was the first major text by Adam Smith who, seven years later, was to publish what was to become one of the major economic classics, The Wealth of Nations (1776). However, Smith regarded The Theory of Moral Sentiments as his most important work because in it he identified the profound human instinct to act not necessarily in self-interest but through, as he phrased it, a ‘mutual sympathy of sentiments’.

In this “eloquent understanding of how death is viewed through many spiritual traditions” (Publishers Weekly, starred review), Bart Ehrman recounts the long history of the afterlife, ranging from The Epic of Gilgamesh up to the writings of Augustine, focusing especially on the teachings of Jesus and his early followers. He discusses ancient guided tours of heaven and hell, in which a living person observes the sublime blessings of heaven for those who are saved and the horrifying torments of hell for those who are damned.

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.

This philosophical essay is the development of a lecture on probabilities which I delivered in 1795 to the normal schools whither I had been called, by a decree of the national convention, as professor of mathematics with Lagrange. I have recently published upon the same subject a work entitled The Analytical Theory of Probabilities. I present here without the aid of analysis the principles and general results of this theory, applying them to the most important questions of life, which are indeed for the most part only problems of probability.

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."

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’.

In 1831, Alexis de Tocqueville, a young French aristocrat and civil servant, made a nine-month journey through the eastern United States. The result was Democracy in America, a monumental study of the strengths and weaknesses of the nation’s evolving politics. His insightful work has become one of the most influential political texts ever written on America.