With the Catholic Church, of all things, turning against the doctrine that maintains there can be a "just war," it's worth taking a serious look at the thinking behind this medieval doctrine, originally based in the divine powers of kings, concocted by a saint who actually opposed self-defense but supported slavery and believed killing pagans was good for the pagans -- an anachronistic doctrine that to this day still outlines its key terms in Latin.
Laurie Calhoun's book, War and Delusion: A Critical Examination, casts an honest philosopher's eye on the arguments of the "just war" defenders, taking seriously their every bizarre claim, and carefully explaining how they fall short. Having just found this book, here is my updated list of required reading on war abolition:
A Global Security System: An Alternative to War by World Beyond War, 2015.War: A Crime Against Humanity by Roberto Vivo, 2014.War and Delusion: A Critical Examination by Laurie Calhoun, 2013.Shift: The Beginning of War, the Ending of War by Judith Hand, 2013.The End of War by John Horgan, 2012.Transition to Peace by Russell Faure-Brac, 2012.Beyond War: The Human Potential for Peace by Douglas Fry, 2009.Living Beyond War by Winslow Myers, 2009.
These are the criteria Calhoun lists for jus ad bellum:
be publicly declared
have a reasonable prospect for success
be waged only as a last resort
be waged by a legitimate authority with right intention, and
have a cause both just and proportional (sufficiently grave to warrant the extreme measure of war)
I would add one more as a logical necessity:
have a reasonable prospect of being conducted with jus in bello.
These are the criteria Calhoun lists for jus in bello:
only proportional means to sound military objectives may be deployed
noncombatants are immune from attack
enemy soldiers must be respected as human beings, and
prisoners of war are to be treated as noncombatants.
There are two problems with these lists. The first is that even if every item were actually met, which has never happened and can never happen, that would not make the mass killing of human beings moral or legal. Imagine if someone created criteria for just slavery or just lynching and then met the criteria; would that satisfy you? The second problem is that the criteria are, as I've mentioned -- just as with President Obama's similar, extra-legal, self-imposed criteria for drone murders -- never actually met.