ABSTRACT
This chapter introduces one of the seminal figures in the historical development of the just war tradition: Francisco Suarez. Suarez follows Aquinas in discussing the notion of just war in the context of charity, in his The Three Theological Virtues: On Faith, Hope, and Charity. Suarez follows Vitoria in approving war in defense of the innocent, noting that "there is no ground for war so exclusively reserved to Christian princes that it has not some basis in, or at least some due relation to, natural law, being therefore also applicable to princes who are unbelievers". When he discusses the law of nations, Suarez concludes that determinations of the substance of our obligations and prohibitions are a matter of natural law and "accordingly, it is from this standpoint that the ius gentium is outside the realm of natural law".
