Full books in PDF format. These are the books that are generally considered standard reading for anybody interested in philosophy. You can find even more primary sources in Philosophy Primary Sources II, and head to the Links section for even more research sources!
Fragments By Anaxagoras of Clazomenae
Summa Contra Gentiles By Aquinas
De Anima (On the Soul) By Aristotle
Nicomachean Ethics By Aristotle
On Interpretation By Aristotle
Posterior Analytics By Aristotle
The Meditations By Marcus Aurelius Antoninus
Three Dialogues Between Hylas and Philonous By Berkeley
A Treatise Concerning the Principles of Human Knowledge By Berkeley
The Consolation of Philosophy By Boethius
The Vagrakkhedikâ Or Diamond-Cutter By Buddha
Meditations on First Philosophy By Descartes
Democracy and Education By Dewey
The Enchiridion, or Manual By Epictetus
Letter to Menoeceus By Epicurus
Principal Doctrines By Epicurus
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
Dialogues Concerning Natural Religion By Hume
An Enquiry Concerning Human Understanding By Hume
Does Consciousness Exist? By James
What Pragmatism Means By James
The Varieties of Religious Experience By James
The Critique of Pure Reason By Kant
Fundamental Principles of the Metaphysics of Morals By Kant
The Critique of Judgement By Kant
Introduction to the Metaphysics of Morals By Kant
Prolegomena to any Future Metaphysics By Kant
Critique of Practical Reason By Kant
An Essay Concerning Human Understanding By Locke
The Second Treatise of Government By Locke
On Subjection of Women By Mill
Thus Spake Zarathustra By Nietzsche
Fragments and Commentary By Parmenides
The Fixation of Belief By Peirce
How to Make Our Ideas Clear By Peirce
Fragments and Commentary By Pythagoras
The Problems of Philosophy By Russell
On the Improvement of Understanding By Spinoza
Fragments and Commentary of Thales
A Vindication of the Rights of Women By Wollstonecraft
Check out Philosophy Primary Sources II and the Links section for even more research sources!