View of North America from Apollo 16, NASA
Dictionary of the History of Ideas. Dictionary searchable by a variety of methods; edited by Philip P. Wiener.
Dictionary of Philosophy and Psychology, ed. James Mark Baldwin. Reprint being developed by Christopher D. Green for Classics in the History of Psychology. Entries A—O complete as of 08.15.03.
Internet Encyclopedia of Philosophy. Edited by James Fieser, general editor, and Bradley Dowden, assistant general editor.
Meta-Encyclopedia of Philosophy. A resource omparing entries from Internet Encyclopedia of Philosophy, Stanford Encyclopedia of Philosophy, Dictionary of the Philosophy of Mind, The Ism Book, The Catholic Encyclopedia (1913), A Dictionary of Philosophical Terms and Names, and the Encyclopedia of Philosophy of Education, maintained by Andrew Chrucky.
Stanford Encyclopedia of Philosophy. A Publication of: the Metaphysics Research Lab, Center for the Study of Language and Information Stanford University, edited by Edward N. Zalta.