Pufendorf: On the Duty of Man and Citizen according to Natural Law

1. It is most agreeable to natural law that men should live in peace with each other by doing of their own accord what their duty requires; indeed peace itself is a State peculiar to man, insofar as he is distinct from the beasts. Nevertheless, for man too war is sometimes permitted, and occasionally necessary, namely when by the ill will of another we cannot preserve our property or obtain our right without the use of force. In this Situation, however, good sense and humanity counsel us not to resort to arms when more evil than good is likely to overtake us and ours by the prosecution of our wrongs.

2. The just causes of engaging in war come down to the preservation and protection of our lives and property against unjust attack, or the collection of what is due to us from others but has been denied, or the procurement of reparations for wrong inflicted and of assurance for the future. Wars waged for the first of these causes are said to be defensive, for the other causes, offensive.

3. One should not have immediate recourse to arms as soon as one thinks oneself wronged, particularly so long as there remains some doubt about right or fact. One should explore the possibility of amicable settlement of the matter by various means, for example by initiating dialogue between the parties, by appealing to an arbitrator, or by submitting the question to lot. The claimant particularly is obliged to try this method, since there is in any case a predisposition to favour possession with some title.

4. Unjust causes of war are either openly such or have some plausible pretext, however weak. Open causes come down to two main types: avarice and ambition, namely lust for wealth and lust for power. Those covered by pretexts are various: they include fear of the wealth and power of a neighbour, unjustified aggrandizement, desire for better territory, refusal of something which is simply and straightforwardly owed, stupidity on the part of a possessor, a desire to extinguish another's legitimately acquired right which the aggressor finds rather inconvenient, and others of this kind.