Catholics and Civil Engagement

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Although developed in the context of thirteenth-century Italy, Aquinas’s theory of law might be considered very modern.  For Aquinas, the function of civil law was not to prescribe everything that is morally right and to forbid everything that is morally wrong (1).  At the same time, Aquinas did not affirm that law and morality have absolutely nothing to do with each other.  According to the medieval philosopher, law has its own, non-arbitrary, moral foundation, which is justice, the common good (2).  It is this that he called ius naturalis—in order to differentiate it from the more comprehensive set of moral virtues, known as lex naturalis (3).  Unlike all other moral virtues, justice is not concerned with moral intentions or with the way an act is carried out by the agent (4).  Rather, it is only concerned with the exterior effects of one’s action on the right order of social relationships, which should be informed by equality, fairness, and solidarity.

1 “Human laws do not forbid all vices, from which the virtuous abstain, but only the more grievous vices … and chiefly those that are to the hurt of others.” Aquinas, Summa Theologica (hereafter ST), trans. by the Fathers of the English Dominican Province, online edition, 2008, I–II, q. 96, a.2.

2 For Aquinas, justice is intrinsically related to the common good. It nurtures the common good by promoting the right relationships without which a community would not exist. Aquinas, ST. I–II, q. 90, a.3; q. 95, a.2; Cathleen Kaveny, Law’s Virtues (Washington, DC: Georgetown University Press, 2012), 50.

3 Aquinas, ST. II–II, q. 57, a.1.

4. “And so a thing is said to be just, as having the rectitude of justice, when it is the term of an act of justice, without taking into account the way in which it is done by the agent: whereas in the other virtues nothing is declared to be right unless it is done in a certain way by the agent.” Aquinas, ST. II–II, q. 57, a.1.


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