A welcome resource for a new generation of readers studying Aquinas, this entirely new Companion explores his philosophical thought in relation to the worldview he inherited, developed, altered, and argued for. To contemporary philosophers, the book reveals the strong connections between Aquinas's interests and views and their own.

1. Banach spaces; 2. The classical Banach spaces; 3. Hilbert spaces; 4. Duality; 5. Bounded operators; 6. Spectral theory; 7. Compact operators; 8. Bounded operators on Hilbert spaces; 9. The spectral theorem for bounded normal operators; 10. The spectral theorem for unbounded normal operators; 11. Boundary value problems; 12. Forms; 13. Semigroups of linear operators; 14. Trace class operators; 15. States and observables; Appendix A. Zorn's lemma; Appendix B. Tensor products; Appendix C. Topological spaces; Appendix D. Metric spaces; Appendix E. Measure spaces; Appendix F. Integration; Appendix G. Notes; References; Index.

Jan van Neerven holds an Antoni van Leeuwenhoek professorship at Delft University of Technology. Author of four books and more than 100 peer-reviewed articles, he is a leading expert in functional analysis and operator theory and their applications in stochastic analysis and the theory of partial differential equations.