Stich, Stephen, John M. Dorism, and Erica Roedder. “Altruism.” In The Moral Psychology Handbook. Edited by John M. Doris and The Moral Psychology Research Group. Oxford University Press, 2010. ISBN: 9780199582143.
Fehr, Ernst, and Urs Fischbacher. “The Nature of Human Altruism.” Nature 425, no. 6960 (2003): 785–91.
Wireless Philosophy. “PHILOSOPHY—Religion: The Problem of Evil.” May 28, 2013. YouTube.
Image of the Cave in the Republic.
Plato. The Allegory of the Cave (PDF). Translated by Thomas Sheehan.
Nails, Debra. “Socrates.” Stanford Encyclopedia of Philosophy. Edited by Edward N. Zalta, March 2014.
D’Ancona, Cristina. “Greek Sources in Arabic and Islamic Philosophy.” Stanford Encyclopedia of Philosophy. Edited by Edward N. Zalta, October 2013.
El-Abbadi, Mostafa. “Library of Alexandria.” Encyclopædia Britannica, May 2016.
Derveni papyrus—information about the oldest Greek papyrus.
