75 The indispensable presupposition, without doubt, of all peaceful intercourse between nations, and the very soul of the juridical relations in force among them, is mutual trust: the expectation and conviction that each party will respect its plighted word; the certainty that both sides are convinced that "better is wisdom, than weapons of war" ( Ecclesiastes ix. 18), and are ready to enter into discussion and to avoid recourse to force or to threats of force in case of delays, hindrances, changes or disputes, because all these things can be the result not of bad will, but of changed circumstances and of genuine interests in conflict.
Source: Summi Pontificatus (Vatican.va)