Aquinas on Evil: Four Comforting Insights

The days are evil, so says Ephesians 5:16.

That statement certainly seems true these days, given the many natural and moral evils running rampant.

In such times, it’s helpful to reflect on the limits of evil, especially when compared to the greatness of the good. In the First Part of the Summa, in Questions 48 and 49, St. Thomas Aquinas examines the question of evil, identifying several truths about the nature of evil that ought to be comforting to all of us.

Evil has no real being

The first thing is that evil has no real being. This doesn’t mean that evil doesn’t exist or isn’t real. Instead, it refers to the reality that evil only exists as a privation of the good, as the classic formulation goes. The example Aquinas gives is of blindness. The condition is a kind of evil that results in the deprivation of one’s ability to see. So it’s not so much a thing as much as the absence of a thing.

Because evil has no real being of its own, it must feed off the good like a parasite.

Aquinas follows this insight to its conclusion. In a moral context, evil can make its effects felt if it is joined to some good in addition to the good it is depriving of its goodness. Take the example of a heavy drinker. The evil is not the privation of the good of reason alone, but “the delight of sense without the order of reason.” (See Question 48, Article 1, Reply to Objection 2.)

Although it is scary to think that evil preys upon goodness, there is a comforting upside to this: it means evil has no real existence on its own.  

Evil cannot destroy the good

One logical consequence of the above is that evil can never wholly destroy the good. The point follows from the fact that evil relies on the good for its existence. Therefore, “if the wholly evil could be, it would destroy itself,” Aquinas says, quoting Aristotle’s Ethics. (See Question 49, Article 3, Answer.)

It is a great consolation to know that no matter had bad things get, evil can never wholly triumph over the good. Even if it appears that evil has the upper hand, evil cannot eliminate the good—it needs it too badly.

Perhaps, in this truth, is hidden a great lesson for us: if evil needs the good, how much more should we seek after the good!

Evil isn’t a real cause

Only things which have being, that is good things, can be causes. So it follows that evil cannot be a real cause, according to Aquinas. He explores the four kinds of causes, concluding that the three main types are associated with the good.

First, there is the efficient cause, which sets things into motion—the carpenter building the table, the kid kicking the soccer. The formal cause is the ‘form’ or blueprint of the thing—the design for the table, the circular shape and structure of the soccer ball. The final cause is the end or purpose for which a thing exists. Matter itself is also good because it has the potential for goodness, according to Aquinas. (See Question 49, Article 1, Answer.)

One might wonder if this is really true. It might not seem like so at first blush.

The key truth on which Aquinas is working off is the inherent goodness of created nature, as God Himself declared in Genesis 1. Our desires for marriage, nourishment, and financial security are natural and good. They become evil when they are depart from their intended purpose—lust, gluttony, and greed. In this way a good can indirectly become a cause of evil.  

The fact that evil is not a cause of things offers some comfort. As much evil as there is in the world, it is more effect than cause. The world, at its foundations, is good. As disappointing as it is to realize how broken our world is, that’s far better than believing it is broken by design.

There is no supreme evil

All of the above leads to final revelation: there is no supreme evil.

This may seem surprising to us. What about Satan?

But think about what it would mean if Satan was the supreme evil. It would mean good and evil are evenly matched. You don’t need a degree in theology to know that’s fundamentally wrong.

There are four reasons why there can’t be a supreme evil.

First, since only good can cause things, that means that good effectively ‘crowds out’ the possibility that evil could exist on par with it. For Aquinas, the ultimate reason this is true is that God, as the supreme good, is the cause of all things, so there’s no room for supreme evil as a cause.

Second, the supreme good, which is God, is essentially or completely good. But there can be no such thing as an essentially evil thing since, as noted above, evil always relies on the good like a parasite on its host.

Third, evil cannot never truly eliminate good without destroying itself. That means there must also be some residue of the good in everything and therefore never any supreme or absolute evil. As Aquinas puts it, “But there cannot be a supreme evil; because, as was shown above, although evil always lessens good, yet it never wholly consumes it; and thus, while good ever remains, nothing can be wholly and perfectly bad.”

Fourth, evil doesn’t have a first principle—an ultimate cause—the way good things go. Evil, by its very ‘nature,’ counts on the good as a cause, as explained above. (See Question 49, Article 3, On the Contrary and Answer; readers who check Aquinas may note that I have an extra reason. That’s because I am counting the On the Contrary as the first reason.)

Again, this should be a great comfort to us: as bad as evil is, there is no supreme evil out there. Evil cannot be greater than the good—not only because of the greatness of the good but because evil by its very nature depends on the surpassing greatness of the good.

image: Apotheosis of Saint Thomas Aquinas by Lippo Memmi and Francesco Traini via Sailko / Wikimedia Commons (CC BY 3.0).

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Stephen Beale is a freelance writer based in Providence, Rhode Island. Raised as an evangelical Protestant, he is a convert to Catholicism. He is a former news editor at and was a correspondent for the New Hampshire Union Leader, where he covered the 2008 presidential primary. He has appeared on Fox News, C-SPAN and the Today Show and his writing has been published in the Washington Times, Providence Journal, the National Catholic Register and on and A native of Topsfield, Massachusetts, he graduated from Brown University in 2004 with a degree in classics and history. His areas of interest include Eastern Christianity, Marian and Eucharistic theology, medieval history, and the saints. He welcomes tips, suggestions, and any other feedback at bealenews at gmail dot com. Follow him on Twitter at

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