The Philosophy of Tolkien: The Worldview Behind The Lord of the Rings (ISBN 978-1-58617-025-7) is a scholarly reference book written in 2005 by Peter J. Kreeft, and published by Ignatius Press (San Francisco).
The book is a discussion of the philosophical skeleton and hidden worldviews of J.R.R. Tolkien's mythology, mostly of The Lord of the Rings, as gleaned through quotes from Tolkien himself from his letters and through frequently-made inferences from the original text.
The book is comprised of thirteen chapters, each pertaining to a philosophical angle or area (e.g. "Angelology", "Ethics: The War of Good and Evil", and "the Philosophy of Language"), a conclusion following them, and then after a bibliography is a concordance where over thirty philosophical dilemmas (e.g. "Duty versus Utility", "Obedience to Authority", "Courage", "Longing (especially for the Sea)", "Knowledge by Faith"), virtues, and vices are matched with references in the books of the trilogy.