Aristotle's Nicomachean Ethics

The second way that our definition of justice ought to be defined is as a personal attitude of respecting the rights of others. One of the major shortcomings of Aristotle’s ethical theory is that he failed to give an account of rights and duties. For Aquinas, a right is defined as “something proper due to each class of person in respect of his particular office” (ST II-II. Q57. A4). Although neither Aristotle or Aquinas gave a sufficient account of rights, moral and political philosophers would go on to define rights in terms of their correlativity with perfect duties. As explained by many modern moral philosophers, a person is said to have a right if and only if society has a corresponding duty prohibiting the violation of the right of that
In the Nicomachean Ethics, Aristotle strongly advocated for this idea. In Book I of the Nicomachean Ethics, Aristotle states, “since happiness is an activity of soul in accordance with perfect virtue, we must consider the nature of virtue…[as] to make fellow citizens good and obedient to the laws” (Becker #). For Aristotle, since the law aims at the common good, and those just acts that produce and preserve virtues are contained in the law. It necessarily follows that the just individual ought to respect and follow the law. Building on this argument, Aquinas argues, “and since it belongs to the law to direct to the common good…it follows that justice…is [acting] in harmony with the law which directs the acts of all the virtues to the common good.” (ST II-II. Q58. A5). For Aquinas, the “law extends over the other virtues” in order to command us to perform the actions that would legally bind our actions to be in accordance with perfect virtue. (ST II-II. Q58. A9). To this effect, Aristotle argues that “all lawful acts are in a sense just acts” because they are aimed at the “common advantage of all” (Becker #). Thus, legislators enact laws that direct individuals to particular virtues in order that they might habituate people to be fair and just. Therefore, to be just, we need to follow the law so that it
For Aquinas, actions are just in that they exhibit virtue and unjust as they exhibit the opposite, which Aquinas calls “general vice” (ST II-II. Q59. A1). Building on this, Aquinas gives two examples of the general vice: legal injustice and inequality. Aristotle simply defines the lawless man as unjust and law-abiding as just. (Becker #). Expanding on this definition, Aquinas argues that unlawful people are unjust because they act contrary to that which is for the common good. As argued above, legislators make laws that direct individuals to develop fairness and virtues in order to direct people to the common good. Thus, for Aquinas, legal injustice is that which is the opposite of legal justice or anything that goes against the common good. Thus, anyone who breaks the law goes against the common good and is thus acting unjustly. Therefore, the first definition of justice in this sense must be anything that is unlawful.
The second kind of injustice for Aquinas is inequality. In respect to this idea, Aristotle states, “the unjust is unequal, just is equal, as all men suppose it to be, even apart from argument” (Becker #). Yet, Aristotle does not provide an argument in the Nicomachean Ethics for inequality as a form of injustice. As such, Aquinas expands this idea by defining inequality as that state in which “more or less [is] assigned to some person than is due to him” (ST II-II.