Abstract
This document covers the following aspects: Thomas Aquinas, Summa Theologica, Michael Walzer, Just and unjust wars and the rules of war. All these sections are based on the Doctrine of double effect from the article from Stanford Encyclopedia of Philosophy. Considering that the Christian thought has a major role in the Just War Tradition which basically is the moral framework which determines most decisions made by both States and soldiers in wartime, I thought it would be interesting to see more in depth what it consists of. Therefore Thomas Aquinas' views about war are going to be very useful in the following analysis. Reading these texts, a second observation that I have made is that it is very complicated to apply the same moral judgments to individuals and collectives. That is one of the reasons why I decided to give a special importance to the Doctrine of Double Effect (DDE) debate which originally only concerned the individual level. War-related issues have led to concern the collective level. We also discuss Walzer's chapter about the rules of war, as Walzer addresses the question of the distinction between these two levels and tells us a lot about the importance of codes and conventions in warfare.
