The debate that lasted on and off from 1511 until the early seventeenth century was initially, as Francisco de Vitoria phrased it, an attempt to explore the right (ius) of the barbarians subjected to Spanish rule. Vitoria pointed to issues that have still not been resolved about the right of any people to impose upon others what it believes to be the natural rights of all humankind. Rome demonstrated that a conquest could only be justified if it were the outcome of a just war. Vitoria employed two more natural law arguments in favor of the conquests, both of which make broad general assertions that were to have a lasting impact on all subsequent thinking about the legitimation of the intervention of one state in the affairs of another. The Roman law of vicinage, to which Vitoria alludes, required that neighbors support each other in times of crisis.