In the first passage, Contarini had discussed two senses of the term “justice”; he now adds a third (still working from the classical tradition), the metaphorical “justice” of a mind whose powers are all in harmony with one another, where the lower parts obey the higher, and the higher is in a state of rectitude. (This “justice” has to be called “metaphorical” rather than “proper” because, properly speaking, justice has to be directed outward, toward another, which is not the case for internal harmony of mind.)
There are two main classical sources for what he treats here: Plato’s Republic and Aristotle’s Nicomachean Ethics.
But we are not speaking here about these two “justices”; when we say that a man is justified, we say something more noble and majestic. In addition to these two senses of “justice,” there is also another type of justice, which Plato treats most fulsomely in the ten books that he wrote on the just, which are also customarily called the Republic of Plato. But Aristotle only touches on this type of justice in the fifth book of the Nicomachean Ethics, which he calls “justice” metaphorically so-called. This “justice” is established in the powers of our mind; and although these [powers] belong to the same mind, and for that reason “justice” properly so-called, which is virtue directed toward another, cannot exist in them; since, nevertheless, these powers of the mind differ among themselves, and a certain measure is owed to each of these, in proportion to the other powers that are its companions (and, if it is perverted, each one’s own is not bestowed upon each of the parts of the mind), and on that account the “justices” maintain themselves reciprocally: justice will exist in them [that is, the powers of the mind] at that time when each one stands steadfast in the measure established for it by nature, such that, namely, the reason commands, but the inferior powers of the mind obey the reason, and the reason is in a state of rectitude [ratio recta sit]. 1 This “justice” is the parent of all virtues, and a virtue in a more noble way than the previous two. (De Iustificatione, p. 588)