The Double Effect Doctrine in Thomas Aquinas’ Just War

The use of war to expand the limits of Christianity or the limits of the power of the Christian Church was, from an early age, regular. This theme, which over the centuries has been the subject of intense debates among intellectuals who tried to justify the morality of this war or, by contrast, served to develop various attacks on the Church, is the focus of the present work. In this way, we seek to understand here the development of the concept of just war in St. Thomas Aquinas Summa Theologiae, it’s way of justifying the use of war, the moments when its use is legitimate, the applicability of the Double Effect Doctrine in this concept and also the influence that his thought exercised on chronologically closer thinkers, but also contemporary philosophy, using to this purpose, the work of Elizabeth Anscombe, a striking figure in twentieth-century philosophy, to understand the pertinence of the medieval theologian thought in this matter.