- Appearance and Reality
- The Existence or Matter
- The Nature of Matter
- Idealism
- Knowledge by Acquaintance and Knowledge by Description
- On Induction
- On Our Knowledge of General Principles
- How a priori Knowledge is possible
- The World of Universals
- On Our Knowledge of Universals
- On Intuitive Knowledge
- Truth and Falsehood
- Knowledge, Error, And Probable Opinion
- The Limits of Philosophical Knowledge
- The Value of Philosophy