For love, thou know’st, is full of jealousy.
—Valentine, Two Gentlemen of Verona (II, 4, 837)

Jealousy, in whatever way it’s taken, arises from intensity of love.
—St. Thomas Aquinas, Summa Theologiae (I-II, 28, 4)

In whatever way it’s taken. St. Thomas, then, was dealing with an ambiguous word. Even in Latin it had a slippery sound—zelus—and its ambiguity would later give rise to two closely related English derivatives: “zealous” and “jealous.” Originally, these meant much the same thing. As zeal was the passionate promotion, so jealousy was the passionate protection, of some beloved person or thing.

Today, of course, we tend to think of jealousy as something wholly negative, but as late as the nineteenth century and even into the twentieth, one could still be jealous in a good way. People still knew, for example, that God was quite right to be “a jealous God” (Ex 20:5), and they didn’t wonder whether St. Paul was guilty of envy when he told the Corinthians, “I am jealous over you with a godly jealousy” (2 Cor 11:2).

Nevertheless, jealousy has always suffered from association with its disreputable tag-along, suspicion, and by Shakespeare’s day this association had become predominant:

For where Love reigns, disturbing Jealousy
Doth call himself Affection’s sentinel;
Gives false alarms, suggesteth mutiny,
And in a peaceful hour doth cry “Kill, kill!”
Distempering gentle Love in his desire,
As air and water do abate the fire. (Venus and Adonis, 670–675)

The stronger a love, the more it seeks to guard what it loves, and the more it seeks to guard what it loves the more it strangles, by fear and suspicion, both the beloved and its own affection. It’s a paradox of such dramatic potential that Shakespeare devoted an entire play to it: “O, beware, my lord, of jealousy; / It is the green-eyed monster which doth mock / The meat it feeds on” (Othello, III, 3).

To untangle this knot, we may avail ourselves of the distinction, drawn by St. Thomas, between “jealousy of concupiscence” and “jealousy of friendship.” Concupiscent jealousy, as we might expect, is passionate protection of the beloved for what are ultimately selfish reasons—for the lover’s own security, enjoyment, or pride. Thus, though he himself may believe otherwise, a thoroughly concupiscent lover is protective not so much of the person he loves, as of his use of that person.

Jealousy of friendship, by contrast, seeks simply the good of the beloved, and so it also seeks to repel—for no selfish motive, yet with great ardor—whatever interferes with that good. Here again, we can think of St. Paul’s “godly jealousy” for the Corinthian church (that is, his fatherly guardianship of their spiritual well-being) or of the prophet Elijah, who, standing alone against the prophets of Baal, was “very jealous for the Lord God of hosts” (1 Kgs 19:10).

Given all this, two things are clear. First, we all begin by loving in ways that are more or less selfish. Our selfish loves are, in fact, the raw material that God gradually transforms, by his grace, into the love of friendship. So let’s not despair: a person who has no concupiscent jealousies is either someone who loves like a saint or someone who doesn’t love at all.

Second, and less comforting, the call to die to concupiscent jealousy, to all forms of possessiveness, is at the heart of the Gospel. It runs all through the Sermon on the Mount, for example, and it’s something Jesus constantly impressed upon the Apostles. Peter’s failure on this point drew his Teacher’s sharpest rebuke (“Get behind me, Satan!”), and when John tried to stop the man who, without permission, was casting out demons in Jesus’ name, our Lord said,

“Do not prevent him. There is no one who performs a mighty deed in my name who can at the same time speak ill of me. For whoever is not against us is for us.” (Mk 9:39–40)

This scene is prefigured in the Book of Numbers, where we find one of the most charming and emblematic stories about that “meekest of men,” Moses. When his faithful aide, Joshua, wanted to stop two men of the Israelite camp from prophesying—they were doing so without authorization—Moses said to him,

“Are you jealous for my sake? Would that all the people of the LORD were prophets! Would that the LORD might bestow his spirit on them all!” (Nm 11:29)

No cramped, controlling, concupiscent jealousy here.

Notice that none of these passages involve, explicitly anyway, the sin of envy, for which jealousy is often mistaken. While jealousy, as we have seen, arises from love of those persons or things we already (in some sense) possess, envy is sorrow that another enjoys some good or excellence that we might possess, but don’t—especially insofar as that good diminishes (or seems to diminish) our own reputation. And, since sorrow at another’s good is directly contrary to charity, envy, unlike jealousy, is always sinful. It is also perhaps the least pleasurable of vices.

In one of his sermons, Ronald Knox says that when we’ve fallen out with someone, one of the best ways to reconcile is to ask for help with something. Why? Because it’s an expression of humility, and it creates a common goal. Perhaps, then, for those of us who suffer from feelings of selfish jealousy or envy, which are rooted in pride and fear, the same advice would prove helpful. The next time we find ourselves possessive or green-eyed, we could give it a try.

Image: Leonardo da Vinci, Genevra de’ Benci