…who attribute that opinion to them; but a closer examination shows that they themselves are at odds and uncertain about the issue, as they are in so many similar questions.

We therefore say: the contention that these propositions do not belong to the realm of certainties is utterly false. On the contrary, they are among the firmest rational certainties. Because assent is always preceded by conceptualization, we must first grasp what we mean by the statement “Justice is good and beautiful, and injustice is evil and ugly,” and then consider whether the predicate truly belongs to the subject. Let us, then, speak about human justice and injustice.

When people declare that justice is good and injustice evil, they mean that justice is something the innate disposition loves; through its very presence it produces delight and joy that benefit both the doer and others, bringing pleasure, happiness, and all that refreshes the soul. Likewise, when they say that injustice is evil, they mean that it harms both the perpetrator and others, that it is detested, engendering pain, grief, and the torments that afflict souls.

It is clear that mankind’s awareness of these propositions—by innate nature and by experience—surpasses its awareness of many medical maxims, such as the claim that scammony purges yellow bile. If experimentally verified statements are deemed certain, how can these—which are far more renowned and have been tested by people far more often—fail to be certain? Those who have experienced their truth are more numerous, better informed, and more reliable; the particular instances occurring in the world are far more abundant, and the reporters who testify to them are likewise more numerous, knowledgeable, and trustworthy.

A person feels within himself a pleasure in justice, truthfulness, knowledge, beneficence, and the happiness that accompanies them, a pleasure he never finds in injustice, lying, and ignorance. People who witness or even merely hear of such virtues—whether or not they themselves attain them—sense in their own hearts a delight, gladness, and joy at the justice of the just, the truthfulness of the truthful, the knowledge of the learned, and the kindness of the beneficent, pleasures absent from injustice, falsehood, ignorance, and wrongdoing. For this reason they feel love for the one who performs those virtues, praise him, and pray for him. They are innately disposed to love such qualities and to rejoice in them, unable to expel that inclination from their souls, just as they are naturally disposed to enjoy eating and drinking and to feel pain when hungry or thirsty.

If those other matters are counted among the certainties known through sense perception and reason—through experience and the like—how, then, could these fail to belong to the class of…