Ortega's response is an original contribution to the psychology of perception. But, as was his habit, Ortega ranges far beyond his ostensible subject; the book may properly be characterized as an heroic attempt to clarify the nature and grounds of truth. It develops ideas contained in his first book, Meditations on Quixote, and introduces new concepts--such as core or nodal problems in any field of inquiry--which would have lasting consequences in his work. This volume includes an appendix, Toward a Philosophical Dictionary, which defines terms important to lectures.