In The Fragility of Goodness. Luck and Ethics in Greek Tragedy and Philosophy, Martha Nussbaum studies significant ethical contents in poetic creation, especially in tragedy. Since there is an ethical dimension in every aesthetic fact and an aesthetic dimension in the ethical problem that is central for Nussbaum, the vulnerability of human excellence, she studies tragedy in the context of the great dilemmas of the fifth century b. C. By these means she enlarges the range of reflection both of ethics as of the understanding of the dramatic text. The purpose of these paper is to show how, taking the texts of the three great tragic poets of ancient Greece as starting point, Nussbaum defends her idea that the tragic conflict is an insoluble dilemma. It also points out the importance of her reinterpretation of aristotelian katharsis as an act of knowledge and not only of purification, and her analysis of the law of revenge as an answer to the vulnerability of human agreements. Finally, since Elizabethan tragedy constitutes one of the peak moments of the tragic in the Western world, this paper seeks to exemplify, following Nussbaum, the ideas of conflict and revenge in some of Shakespeare's tragedies, ideas that may contribute both to the understanding of Elizabethan theatre as to opening this theatre to ethical research.