Ius naturale: The Foundations of Modern Human Rights Discourse in the Natural Legalism of Thomas Aquinas Part II
The previous post in this series examined the distinctions between ‘ius’ and ‘lex’ in Aquinas’ thought and the import of these ideas to modern human rights discourse. Part II will examine further features of Thomistic natural law theories important to modern concepts of rights as well as the problematic of natural slavery in Aquinas’ thought.
Further major, if readily overlooked, resources in Thomistic natural legalism to turn to in search of the foundations of modern human rights discourse are Aquinas’ teachings regarding legislative authority and the related question of tyrannicide. The question of moral authority to legislate is a pressing one in any discussion of human rights. To Aquinas, only just human laws have moral authority and thus only they entail moral obligation because only they have an intelligible relation to the principles of natural moral law. Aquinas does not equate authority with power. He does allow that the legislations of a lawmaker who passes laws that violate the purpose of law retain the character of (positive) law. Such a lawmaker possesses legislative power but not proper legislative authority. Legislative authority is bound inseparably to moral obligation. To say that a person or body possesses legislative authority is, in effect, to say that the laws passed by this person or body are morally binding upon those subject to his/her/its laws. This is a principle of the natural law, for, Aquinas holds, the same judgement of the common good which calls legislators with authority calls to the same extent for compliance with laws. However, legislative authority it not held unconditionally. When a lawmaker forfeits the moral authority to legislate by passing laws which enjoin unjust acts then the moral obligation of those theoretically subject to obey is, in fact, to disobey the unjust law. By the same token, laws which purport to authorise unjust acts are morally invalid and are thus of no effect, so the theoretically subject are not obligated to obey them. Unjust laws, while they may retain the character of positive law, are, inasmuch as they are discordant with the natural law, not so much laws as acts of violence and are not binding of the conscience of those theoretically subject to them. There is an important proviso upon this judgement, however: unjust laws may still bind the conscience if disobedience might cause public disorder or demoralisation, or would lead others into wrongdoing. The risk of such publics harm can, to Aquinas’ mind, oblige one to forfeit one’s rights vis-à-vis the unjust law.
Related closely in Aquinas’ mind to the issue of legislative authority is the question of tyrannicide, or, more broadly, the right to overthrow an unjust ruler or rulers. Aquinas’ writing on the right of tyrannicide can be said to contain a proto-doctrine of popular sovereignty. Aquinas draws his definition of tyranny from Aristotle as rule for the benefit of the ruler(s) rather than the common good. This definition is to be found in Aquinas’ discussion of the sin of sedition and it makes clear that tyranny violates the natural order of the relationship between the ruler(s), who govern(s) for the public good, and the ruled, who, in exchange, abide by the laws set forth by the ruler(s). This is why taking up arms against a tyrant is not an act of sedition, since the tyrant is already guilty of sedition through the acts of tyranny. The victims of tyranny thus have a right to take up arms against and to overthrow the tyrant. While this right of tyrannicide is a far cry from the popular sovereignty of Locke or Rousseau but it does contain the kernel of the core principle of that theory, the consent of the governed. Aquinas allows that in cases when the ruler violates proper legislative authority and governs out of self-interest rather than for the common good, in violation of the natural law, the governed, who by virtue of that violation of the natural law are not morally bound to obey the ruler, may withdraw their consent to live under tyranny and overthrow the unjust ruler.
While Aquinas’ natural legalism provides many of the foundations of modern human rights discourse his thinking also contains a large problematic that could potentially undo the argument that Thomism lays the foundations of human rights theory. Any argument tracing modern human rights discourse to the work of Aquinas must address the deeply problematising reality of Aquinas’ position on slavery. As noted above, Thomas restricted absolute human freedom and equality to the human soul, which he deemed the ‘greater part’ of the person, and allowed not only for inequality of rank but complete bodily subjugation of one person to another. Aquinas’ position on slavery reflects that of Aristotle and holds that slavery is in accordance with the natural law because it is conducive to the present human condition and is thus ‘natural’ in the Aristotelian sense. Aristotle advanced the notion of persons, even of people, without the faculty of reason, who are thus incapable of prudence and virtue and cannot attain happiness under their own intellectual capabilities. It is natural and for their own good that such persons be enslaved, being born naturally inclined to the condition of servitude. Just slavery, for Aristotle, is the enslavement of those naturally inclined to servitude by faculty faculties of reason by those more fit to govern them, so long as the enslavement serves the welfare of the slave (which in effect means that the slave is well-treated in his or her enslavement). Aquinas adopts this position that slavery is a natural result of the superiority in virtue of the master over the slave and the superior ability of the virtuous natural master to govern the vicious natural slave over the natural slave’s faculties of self-governance. Aquinas even extends this position to slaves taken as prisoners of war, on the grounds that victory in war reflects a pre-eminence in virtue.
Despite the problematic nature of Aquinas’ thought on slavery his work was applied by later interpreters as the grounds for the abolition of the institution. Perhaps most importantly, Francisco de Vitoria in his work De Indis argued against the enslavement of the indigenous inhabitants of South and Central America using the Thomistic principle that rational beings, which Vitoria considered the ‘Indians,’ as they were known, to be, possess dominion over themselves and thus cannot be enslaved. Like Aquinas, Vitoria accepted the concept of ‘natural slavery’ as posited by Aristotle but applied the conditions of the natural inclinations to servitude which, according to Aristotle and Aquinas, are required of just and natural enslavement and argued that the American aboriginals did not meet those conditions. Vitoria’s application of Thomism to the problem of the enslavement of indigenous American populations makes clear that despite the problematic of Aquinas’ own views on slavery Thomistic natural law theory can and has been applied in opposition to slavery. While modern human rights discourse not does allow for the categories of ‘natural slavery’ on the grounds posited by Aristotle, Aquinas, and Vitoria, and indeed rejects categorically the enslavement of any human being, Aquinas’ strict requirements for the practice of slavery to the natural outweigh his personal endorsement of the possibility that slavery can, indeed, be natural, by positing conditions for the person to be enslaved which no human being, or, likely, any rational agent, actually meets. This is not to say that Vitoria has ‘overcome’ the problematic of Thomistic natural slavery but his work does prove that Thomistic natural legalism contributed historically to abolitionism and thus to human rights discourse generally.
Though Aquinas did not think or write in terms of ‘human rights’ as they are discussed today and it would be anachronistic to impose such a concept on his thought, his ethical and legal works were extremely influential in the development of modern human rights discourse. He was not the only important medieval thinker in this movement, other Scholastic theologians like Duns Scotus and, in particular, William of Ockham, also made important contributions to the tradition, but his influence over later Scholastic and humanistic thinkers like Vitoria, Suaréz, and Grotius, who contributed more directly to the tradition in their writings on slavery, sovereignty, and international law, make his theories extremely important in the history of the Western tradition of human rights discourse. Aquinas’ theories of justice; natural right; legislative authority; and tyrannicide, which contains a proto-doctrine of popular sovereignty, are based in his natural legalism, provide some of the primary foundations for human rights discourse through their advancement of the implications for a just, fair social order and just governance as required by humanity’s innate dignity as rational agents and by the natural law. While Aquinas did endorse the idea of ‘natural slavery,’ in line with his Aristotelianism, the application of his work to the very question by Francisco de Vitoria established that this difficulty is not insurmountable, since Aquinas’ own arguments on the question can be brought successfully to bear in favour of abolition.
Part III of III will comment upon the continuing relevance of Thomistic thought for modern human rights and argue why the Thomistic background of the modern tradition of human rights discourse ought to be taken into account in contemporary rights and rights-based debates.
Notes and Bibliography
 Finnis, John, Aquinas: Moral, Political, and Legal Theory (New York: Oxford University Press, 1998), 266.
 ST I-II.92.1
 Finnis, Aquinas, 269.
 The loss of legislative authority is effectively synonymous in Aquinas’s writings with the passing of an individual unjust law. Thus legislative authority can be thought of as being held only on condition of its proper use.
 ST I-II.96.4
 ST II-II.57.2
 Finnis, Aquinas, 273.
 ST II-II.42.2 adv 3
 Finnis, Aquinas, 290.
 Killoran, John B., “Aquinas and Vitoria: Two Perspectives of Slavery,” in Johnson, Harold J., ed, The Medieval Tradition of Natural Law (Kalamazoo: Medieval Institute Publications, 1987), 89.
 Capizzi, Joseph E., “The Children of God: Natural Slavery in the Thought of Aquinas and Vitoria,” Theological Studies 63 (2002), 34.
 Capizzi, “The Children of God,” 35.
 Killoran, “Aquinas and Vitoria,” 89.
 Killoran, “Aquinas and Vitoria,” 94. Cf. ST I-II.1.1 adv 2; ST I-II.6.2
 Capizzi, “The Children of God,” 51.