Primary Sources – Modern Philosophy Three Dialogues Between Hylas and Philonous by George Berkeley A Treatise Concerning the Principles of Human Knowledge by George Berkeley Discourse on the Method of Rightly Conducting the Reason and Seeking for Truth in the Sciences by René Descartes Meditations on First Philosophy by René Descartes Democracy and Education by John Dewey Ideas and Opinions by Albert Einstein Essays of Ralph Waldo Emerson The Vocation of Man by Johann Gottlieb Fichte The Science of Knowledge by Johann Gottlieb Fichte On Sense and Reference by Gottlob Frege The Thought: A Logical Inquiry by Gottlob Frege The Phenomenology of Spirit by G.W.F. Hegel The Philosophy Of History (Introduction) by G. W. F. Hegel Philosophy Of Mind: Part Three of the Encyclopaedia of the Philosophical Sciences by G.W.F. Hegel Being and Time by Martin Heidegger The Question Concerning Technology & Other Essays by Martin Heidegger What is Metaphysics? by Martin Heidegger Dialogues Concerning Natural Religion by David Hume An Enquiry Concerning Human Understanding by David Hume An Enquiry Concerning the Principles of Morals by David Hume A Treatise of Human Nature by David Hume Practical Philosophy of Immanuel Kant The Critique of Pure Reason by Immanuel Kant The Critique of Practical Reason by Immanuel Kant The Critique of Judgement by Immanuel Kant Introduction to the Metaphysics of Morals by Immanuel Kant Fundamental Principles of the Metaphysics of Morals by Immanuel Kant Prolegomena to any Future Metaphysics by Immanuel Kant Fear and Trembling by Søren Kierkegaard The Sickness Unto Death by Søren Kierkegaard Philosophical Fragments by Søren Kierkegaard Monadology by Gottfried Wilhelm Leibniz An Essay Concerning Human Understanding by John Locke Utilitarianism by John Stuart Mill Principia Ethica by G.E. Moore On the Genealogy of Morals by Friedrich Nietzsche The Portable Nietzsche edited by Walter Kaufmann Thus Spake Zarathustra by Friedrich Nietzsche The Age of Reason by Thomas Paine Pensées by Blaise Pascal The Fixation of Belief by Charles Sanders Peirce How to Make Our Ideas Clear by Charles Sanders Peirce The Confessions of Jean-Jacques Rousseau The World as Will and Representation – Vol. 1 by Arthur Schopenhauer The World as Will and Representation – Vol. 2 by Arthur Schopenhauer The Basis of Morality by Arthur Schopenhauer Note: You can find 135 free philosophy e-books and free online philosophy courses at Open Culture. Project Gutenberg and Internet Archive both host vast libraries of e-books for free to the public.