1. The subject must be of great consequence. It is criminal, for a frivolous cause, to expose men to all the evils that accompany a war, even the most fortunate. 2. There must be some probability of success: for it would be criminally rash to expose one's self foolhardily to certain destruction and, to avoid a lesser evil, throw one's self into a greater. 3. If we had no gentler means at our disposal. There are two ways of settling a dispute between nations, without recourse to arms: 1, an _amicable conference_ between the parties; 2, the intervention of a disinterested third party, or _arbitrament_. A third means, much rarer and now abandoned, is that of _casting lots_. When all the means of settling the difficulty amicably have been exhausted, there remains, before taking up arms, a final obligation, namely, to declare to the enemy the resolution of employing the last means: this is what is called a _declaration of war_. =117. Duties in times of war.=--War having become a sad and unavoidable necessity between nations, and the use of force determined on, it behooves as much as possible to restrict it in its effects, and to reconcile the rights of humanity with those of justice. Hence, certain rules established by jurisconsults who have treated these matters, and notably Grotius, the founder of international law. The fundamental principle of the right of war is the following: All that has a morally necessary connection with the purpose of the war is allowed, but nothing more. In fact, it would be wholly useless to have the right to do a thing, if, to accomplish it, one could not employ the necessary means thereto; but, on the other hand, it would not be just if, under the pretext of only defending one's rights, one should believe that everything is permitted, and should resort to the last extremities. From this general principle are deduced the following consequences, which are only its applications: 1. It is certain that it is lawful to kill the enemy's soldiers, and, in fact, the purpose of the war being to constrain the enemy to recognize the justice of our cause, it would be vain to take up arms if one could not use them. It is then one of the cases where manslaughter may be considered innocent, and justified by the right of personal self-defense. (See above, Ch. iii., p. 50.) 2. However, the right of death upon the enemy has its limits. As a principle, it only extends to those who carry arms, and not to private individuals who do not defend themselves, arms in hand. Such can only accidentally become the victims of the war: for instance, it is impossible in a battle to protect the inhabitants of a disputed village against the balls of either party; but we should not knowingly strike dead those who do not defend themselves. 3. Strangers should be allowed to quit a country exposed to war; and if obliged to stay, they should be no further exposed than to share its inevitable perils with the other citizens.