"When you go to war against your enemies..."(Deuteronomy 20:1)
Chapter 20 of Deuteronomy prescribes a number of rules about going to war. From what we learn in the Torah itself and in the books of Former Prophets, the Israelites often were at war. Thus these rules, even if they seem arcane to us, probably guided our ancestors in their wars.
The next group of precedents we hear about war, though, are in the Mishnah and Talmud, which were written at a time when Jews were not ruling themselves and had no power to decide when to go to war and how to wage it. That is even more true for medieval sources (especially Maimonides' "Laws of Kings" in his Mishneh Torah) and for Jews writing in the early modern period. Jews often were conscripted to serve in the king's army, but they had no control over what wars to fight and how. Many of us know that our grandfathers or great-grandfathers fled Russia - or had one of their toes cut off - precisely to avoid serving in the Czar's army.
Two events have changed this pattern. The Enlightenment and its political aftermath in Western countries, beginning in some places in the seventeenth century and continuing in many more nations to our own time, have meant that we Jews are full citizens and sometimes even serve in government positions. This means that we have a responsibility actively to engage in deciding which wars to wage and how, even if we do not control what our nation does. The establishment of the State of Israel imposes this responsibility even more starkly, for there Jews, as the majority, do decide these matters of policy and military conduct.
But how can we gain moral guidance from our sources? After all, the most ancient ones do indeed come out of real experience in the field of battle, but the military and political realities of their time are significantly different from our own. Sources after the First Temple period, except for the century or so of the rule of the Hasmoneans, were written in a vacuum of experience of deciding when and how to fight a war, so either our sources are too old to be relevant or too lacking in the actual experience of waging a war to be trusted.
It should be noted that the same critical methodological question arises in other areas of life as well. How, for example, can we gain moral guidance from our tradition about medical matters when modern medicine is so radically different from that of even a century ago? And how can we gain moral guidance from our tradition about business when our sources speak primarily about local markets and we now make transactions in an instant across the nation and the world and when we now have corporations, which our ancestors never knew?
There are logically at least three responses to this crucial question of method. On one end of the spectrum, one could say that if the tradition does not address a problem in its modern guise or maybe even at all, we should say that the tradition has nothing to tell us. So, in our example, we would then say that Judaism can tell us nothing about whether, to use one of President Obama's recent statements, the use of chemical weapons should automatically trigger intervention in another country or how to deal with nuclear weapons. The advantage of this approach is that it is honest: Jewish sources know nothing about chemical or nuclear weapons and certainly give us no direct guidance about their use. The disadvantage of this approach, though, is that it makes Judaism morally irrelevant to much of contemporary Jewish life, and that undermines one of the most important reasons why Jews are interested in their tradition in the first place - namely, to give them moral guidance.
The opposite end of the spectrum is a version of Ben Bag Bag's statement in the Mishnah: "Turn it over, and turn it over again, for everything is in it" (Ethics of the Fathers 5:22). That is, by hook or by crook we must make the text tell us what we are supposed to do. Because our sources do not directly deal with chemical or nuclear weapons, we need to read them out of context to mean what they could not possibly have meant originally. This is dishonest. Further, because the text is not controlling what we make of it, we are really imposing our own views on the text rather than deriving the text's message for us from it (eisegesis rather than exegesis), and so we are actually getting no guidance from the text at all. At best, we are pretending to gain authority for our own views. On the other hand, this method does tie our decisions to the tradition, thereby giving them authority and giving the tradition relevance, tortured though the path back to the tradition may be.
So to use the tradition honestly and also fruitfully to address our modern moral problems, I would suggest a third method. When our tradition does speak to a specific issue we have, we should definitely use it at least to begin our moral discussion and often to determine its outcome. In the many cases, though, where our tradition could not have known modern realities, let alone dealt with them, we should do "depth theology," where we identify the underlying concepts and values of our tradition and then apply them to the question at hand. We may disagree, of course, as to how to do that, but we Jews are used to disagreeing even about how to interpret and apply texts that directly relate to modern issues. In this way, we can, I think, create a decidedly Jewish and decidedly relevant and wise response to war and all the other issues in which we consult our tradition for moral guidance.
Shabbat Shalom.
For more on Jewish ethics and war, see Elliot N. Dorff, To Do the Right and the Good, Chapter Seven, and Elliot N. Dorff and Danya Ruttenberg, eds., Jewish Choices, Jewish Voices: War and National Security. For more on the methodology described here, see Elliot N. Dorff, Matters of Life and Death, Chapters One, Two, and the Appendix, and Elliot N. Dorff, For the Love of God and People: A Philosophy of Jewish Law, esp. Chapter Six.