Evil comes in many varieties. A typical list would include: genocide, murder, torture, terrorism, slavery, sadism, the sexual and physical abuse of children, slander, betrayal of trust, desecration of the sacred, disfiguring, maiming, and crippling. We might count as evil the willful destruction of great works of art or architecture, in addition to such standard examples as the extermination of innocent populations. Physical harm to persons is not always involved, though it often is, along with emotional pain. Given this variety, we might be tempted to suppose that the class of evil acts is irreducibly heterogeneous, united by nothing more than brute disjunction or family resemblance. That is, we might deny that there is any one feature common and peculiar to all evil acts. The concept of evil, it may be said, is just too vague and open-textured to admit of informative definition. We must accordingly accept the diversity of evil.
I shall suggest, to the contrary, that evil is a unitary quality common to all acts rightly classified as evil. Moreover, it is quite a simple quality, which is not to say that it is easily identified in practical life. My definition of evil, to get right to it, is that it is the intentional destruction of the good—but this will need some unpacking. First, destruction: by this I simply mean, “causing to cease to exist”. The world contains a certain entity or quality at a certain time and to destroy that entity or quality is to bring about its cessation. This may be done violently or insidiously, quickly or slowly. It is the opposite of creation: instead of causing something to exist, it removes that thing from reality. So destruction is explained through the notion of existence and its negation. It is therefore a highly general notion applicable a wide variety of cases—people, animals, artifacts, states of mind, social movements, bits of nature.
Second, the good: by this I mean any good state of affairs. Without going into the matter fully, the following list will serve our purposes (we could add to it if need be): life, happiness, knowledge, innocence, freedom, friendship, and aesthetic quality. If you think some of these items reduce to others, or should not be on the list of intrinsic goods at all, by all means amend as you see fit; the definition of evil will remain the same, even if its extension differs. I favor keeping the list fairly long and non-reductive, because I think that the good is best seen in all its variety; we don’t want theories that try to reduce every basic value to one (such as pleasure). Despite the variety of the goods, there is something they all having in common—that they are precisely good—and that is what matters to the definition of evil.
Third, intentional: by this I mean that the act in question must be intended in a certain way. If an agent destroys something good by accident, through no fault of his own, and is horrified by what he has wrought, he cannot be adjudged evil, merely unlucky. So we should say that an evil act is one that is intentional under the description “destruction of the good”: the agent foresees and intends the destruction of the good and acts as he does in order to bring this destruction about. He “knows what he is doing”. In a typical case he plans the destructive act and self-consciously carries it out.
Thus an evil act is one that involves an agent intentionally destroying what he knows to be good. The mental state of the agent incorporates the concepts of destruction and goodness—this is the content of his intention in acting. It is the intention that defines the evil agent. Is there a second-order intention associated with this first-order intention? Grice argued that communicative acts require a second-order intention—not only the intention to produce a belief in one’s audience, but also an intention that the first intention should be recognized by the audience. Thus the basic intention is transparent, not concealed and secret. In the case of the evil agent, there is also a second-order intention, but it is not a transparency intention—it is an opacity intention. The agent intends that his first-order intention should not be recognized by observers (he may even try to shield himself from knowledge of his intention). The evil agent is trying to destroy the good, but he doesn’t want people to know that this is what he is doing, possibly including himself. Even if he feels safe in his actions, fearing no repercussions, he does not want it to be apparent that his aim is precisely to destroy something good. So he will often characterize his actions in other ways—say, by arguing that he is serving a greater good. I might put it by saying that there is always a level of shame about evil actions, and hence a desire for concealment. The agent is not proud of what he does, even if he tells himself it is somehow necessary. For the agent has set about intentionally destroying what he acknowledges to be good, and this is not something he can happily admit. That is why there is often a degree of self-deception involved in evil actions (not so for virtuous actions). For this reason there will typically be a second-order intention to conceal the first-order intention. The easiest way to fulfill that intention is to commit the evil act secretly, away from prying eyes—as it might be, in a dungeon or concentration camp or in the dark. The evil agent is by nature deceptive; secrecy is his cover, his protection.
The conception of evil I am suggesting limits it to creatures capable of certain kinds of “sophisticated” attitudes. I doubt that animals are capable of evil in the sense I have defined, though they are certainly capable of impressive feats of destruction. Animals may maim or kill but they don’t do so with the kinds of intentions I have described (some of our primate relatives may have such intentions, in which case my claim applies to non-primate animals). They may cause great suffering and death but they do not do so under the description “destroy the good”. They just don’t have the concept. Evil is what results when a creature acquires such abstract concepts, so it is a uniquely human achievement. Perhaps, indeed, the very acquisition of the concept of the good (as well as the concept of destruction) is what opens the human species up to feats of evil not possible for other species. We do evil things precisely because we know what good is; we destroy the good because we apprehend things as good. Evil thus requires a certain intellectual attainment. The necessity to conceal evil acts also requires a cognitive sophistication absent in other animals (possibly with certain exceptions). It is not that animals do less harm than we do—though that is doubtless true—but rather that the harm they do does not spring from evil motives and intentions.
Now we must see how the definition fits the various types of evil I have listed. Let’s start with a hypothetical example. Suppose a university administrator, call her Eva, receives a complaint against a distinguished professor, call him Carl. The complaint is completely fictitious, being motivated by malice and a bad grade. Eva knows this, but she also knows that taking disciplinary action against Carl will, in the current climate, score her political points, help with funding, and appease the radical feminists. She decides to initiate dismissal proceedings against Carl, fully aware that this will ruin his reputation, take away his livelihood, and prevent him from any further achievements as a scholar and teacher. She also knows that he cannot fight her actions legally because it would bankrupt him to do so. Eva thus uses her power, quite cynically, to destroy Carl in order to advance her political and personal goals. Carl is duly forced out of his position, becoming impoverished and bitter. I hope we can agree that Eva was evil in acting as she did, and the reason is clear: she intentionally destroyed something good. Carl was an innocent man, a good man, and also a productive and brilliant scholar. Eva destroyed his ability to work and teach, as well as his happiness and security, along with that of his family. She did so deceptively, unethically, and callously. Her evil actions fit the definition perfectly. 
Next consider an artist who is tired of being unfavorably compared to another artist, whose work is vastly superior. He decides to destroy the superior artist’s work, stealing into his studio one night and burning all his paintings. Let’s suppose that he manages to destroy every one of the great artist’s works and also to prevent him producing any more (he is so traumatized by the destruction). Now the second-rate artist gets more attention and makes more sales, with his main rival eliminated. Again, these actions are clearly evil, and they fit the definition perfectly: the evil artist has intentionally destroyed works of great aesthetic value for his personal gain and out of envy.
David is a bitter man and a failure in life. He lashes out at anyone he can, belittling and insulting people. His young son Patrick becomes a target of his ire because David cannot stand the thought that his son might succeed where he failed. He sets out to damage Patrick psychologically, even going to the extreme of raping his five-year old son. He succeeds in his aim and Patrick is so traumatized that he becomes a heroin addict and eventually commits suicide. Again, the evil is obvious, and again we can see why: David has destroyed Patrick’s innocence and happiness in order to satisfy his own warped needs. His express aim was to prevent his son from achieving anything good in life, including any chance of happiness: he destroys the good in order not to suffer the pangs of his own sense of failure. 
Terrorists bomb a city center, killing dozens of innocent men, women, and children. They do so because the people they have targeted practice a different religion from theirs and appear to be happy and prosperous doing so, making their own religion look shabby and regressive. Their aim is not just to kill and maim but also to undermine the peace of mind of people living in the city in question. Their actions are evil and for the usual reason: they have destroyed life, happiness, and peace of mind among the target population, because of their misguided religious zealotry.
The Nazis undertake a program of mass extermination against the Jews. Their motivation is that the Jews are far too successful in German society, owing to their intellectual and cultural superiority. The Nazis covertly acknowledge the qualities of the Jewish minority and wish to rid themselves of a people that challenge their sense of racial superiority. They accordingly murder six million Jews by means of starvation, gunshots, and poison gas. They are defeated before they can realize their project of total genocide, but they would have carried it through to the end if they could. No one can doubt the evil of the Nazis, and their actions clearly conform to the theory: they intentionally destroyed the good—life, well-being, culture, achievement—in order to gratify their own (shaky) sense of superiority.
Liz is a friend of Susan, who is also friends with Wendy. But Liz doesn’t like the friendship between Susan and Wendy; she wants Susan to herself. She decides to undermine the friendship between Susan and Wendy by telling lies about Wendy to Susan, to the effect that Wendy has been making advances to Susan’s boyfriend. Liz convinces Susan of this falsehood, using doctored photographs and what not. Susan consequently drops Wendy as a friend, causing her considerable distress. This is not evil on a grand scale, like the previous example, but it is evil nonetheless. Here the good that has been destroyed is friendship.
Iago sets out to destroy Othello, who is respected as a great general and honorable man (Iago’s reasons are obscure), by making him jealous. He succeeds in reducing the normally unflappable Othello to a blubbering heap and a murderer of Desdemona, his wife. Iago’s evil consists in this act of destruction, more of the soul than the body, in the case of Othello. Macbeth betrays the trust of King Duncan, murdering him while he sleeps, in order to advance his own ambitions, and then murders others to cover his crime. He doesn’t think Duncan is a bad king; on the contrary, he likes and admires Duncan. So he has knowingly destroyed something good. Judas betrays Jesus, despite believing him to be the Son of God, for fifty pieces of silver; he thus destroys the embodiment of goodness for a tawdry sum.
I don’t think I need to multiply examples any further: it is easy to see how the definition of evil I have presented works, and indeed it is an intuitive and natural way to characterize evil. The definition is simple and straightforward; and it offers a uniform account of what evil is. Are there any counterexamples to it? Someone might suggest that the definition does not provide a necessary condition for evil, since some evil consists in positively producing harm, not just removing the good. The evil of torture, say, is that it produces a lot of harm, either pain or injury. But I take it that this is just another way to phrase the theory under discussion: to produce harm is just to annihilate a good, i.e. the good of not being harmed. Harms are defined relative to goods: for example, pain is bad because it is good not to be in pain. The trouble with stating the theory in terms of harm is that it loses generality—not all cases involve an intention to harm. The envious artist was not attempting to harm his rival exactly, though he did; his intention was to destroy the good—the harm to his rival was just a by-product. The same can be said of the desecration of sacred sites or buildings. The harm formulation gets the emphasis wrong: the evil agent recognizes the good in something and seeks to destroy it despite this; he is not just out to do harm. A run-of the-mill thug might be out to create harm by punching anyone within range, but he is not evil in the sense I am trying to capture. Evil is the intentional abolition of the good, recognized as the good. Iago, say, is not interested in bringing down some undistinguished nobody; what incites him is Othello’s distinction—the good that he embodies. And what marks Judas out is not just a betrayal of any old goat-herder from Palestine, but the fact that he betrayed the Son of God (allegedly). The harm caused might be the same in both cases, but the evil agent is doing more than just maximizing harm—he is destroying that which is indisputably good. It is true that one way to destroy what is good is to cause harm, as in crippling an athletic rival, but the evil resides in the negation of goodness, not in the harm as such. Nor is it clear that negating the goodness of a person is always harming her: if a scientist reduces the intelligence of a rival by putting a chemical in her drink, this is definitely evil, but it is not clear that the target has been harmed—she might be quite happy having average intelligence. I might set out to make you happier by chemical means, so that you spend less time at home working, and more time out having fun—as a way to lessen your intellectual output. This would be evil, but it is not clear what harm I have done to you—you might even decide you want to change your life-style in that direction anyway. What if I introduce you to a very seductive partner so as to distract you from your important intellectual work—have I harmed you?
Now it might be claimed that the conditions are not sufficient for evil, since it is possible to intend to destroy the good for morally praiseworthy reasons. Thus we have vaccination and surgery—we remove a person’s tranquility and freedom from suffering by subjecting them to these procedures. Are dentists necessarily evil? The obvious answer is that the agent is aiming for the greater good of the patient, and rightly so: the short term removal of the good is justified by the long term creation of the good. It wasn’t that Iago believed that only by destroying Othello and Desdemona could he save the city of Venice from a terrible fate: he did not commit his harmful acts with a heavy heart, with everyone’s best interests in mind. So we should add that evil is the intentional destruction of the good all things considered—that is, when the destruction of one good is not justified by the production of a further good. Of course, this is not to deny that some evil agents use such justifications spuriously, as the Nazis did to excuse their genocidal actions. But in cases like dentistry it is clear that no evil is committed, since the intention is to produce long term dental goodness in the (temporarily) suffering patient. The dentist is promoting the good not negating it.
Let me return for a moment to the destruction of reputation, because I think it is particularly instructive. This does not involve physical harm or death, so it doesn’t fit a crude definition of evil as simply “causing suffering”. A person can no doubt suffer from the unjust destruction of his reputation, but that suffering does not pinpoint wherein the evil lies. The slanderer is taking aim at a manifest good and seeking to annihilate it: the good character or good standing of the person unjustly accused. Suppose the target’s reputation is well earned and fully justified—it is backed by undeniably good qualities. Then the slanderous accuser is attempting to negate this manifest good—say, with a view to preventing the person accused from gaining employment. The intention is precisely to destroy a human good—that is its exact focus. This epitomizes evil, perhaps more clearly than any other case, because the good that is destroyed is specifically targeted as such. It is close to another paradigm of evil—the intentional undermining of trust. If an evil agent sets out to gain the trust of another person, himself without evil intent, by encouraging such trust, with a view to betraying it later, she has attacked a deep and central human good—the ability to trust another person. A person treated in this way may never be able to trust again, which undermines many other human goods. The betrayer has destroyed something precious and precarious, and we rightly reserve our severest criticism for such actions. This is precisely what Iago and Macbeth do. It is particularly heinous because it specifically targets a central human good for annihilation. Just as a person values his good name, so he values being able to trust other human beings: to destroy these things is evil in the purest sense. Neither of these forms of evil is calculated to cause pain or death (though they may cause both of these things); what they are calculated to do is to take a certain kind of good from a person that is highly valued. Both involve depriving the target of normal social relations. The evil here consists in destroying a fundamental social good—being well thought of and kindly received, and being able to place one’s trust in another. Hence these are my paradigms of evil, not the usual cases of torture and murder—because they exemplify the abstract form of evil so clearly.
We need to make a minor amendment to the definition. I have been speaking of evil agents, but there are also those who are passively complicit in evil—bystanders or onlookers. There are not just those who do the deeds, there are those who allow them to be done. It is not only the agents of the action who are evil but also the observers of it: the wife who lets her husband rape his son, those who tolerate atrocities committed by others, people who make no protest when those with power persecute the innocent—the whole sorry crew of cowards, toadies, and the morally numb. These enablers of evil should also be included under the concept. It is easy to do so: just add “or those who tolerate the destruction of the good”. We thus recognize two categories of evil: active and passive.
We should also make a distinction between ideological evil and non-ideological evil. Iago and Macbeth are not evil ideologues, like Stalin or Hitler. They stop when the count of corpses reaches the double figures, and no general ideology drives their homicidal tendencies. But the evil ideologue envisages a much wider field of operations—sometimes totaling in the millions. Here entire sections of the population are targeted for destruction: Jews, gypsies, homosexuals, the bourgeoisie, heretics, racial minorities, and many others. The guiding ideologies are by now very familiar to us, but it is easy to miss them when they emerge, because they masquerade as moral crusades. It is often only in retrospect that an evil ideology reveals itself for what it is. Ideological evil allows people to destroy the good while telling themselves they are working for a greater good, so it is especially sinister and dangerous. They make people think that their evil acts are not evil at all. Whenever you see people justifying destructive acts by reference to an ideology be on the lookout for ideological evil. One sees in the ideologue a wild-eyed enthusiasm, a disregard for basic principles of fairness and justice, violent imagery and extreme response, blanket condemnation, sloganeering, demonizing, prejudice and pre-judgment, sectarianism, and social conformity. The psychology of ideology is murky, but the human mind clearly has a weakness for ideology, and the results can be devastating (consult history). I don’t doubt that one of their principal attractions is that they permit people to do evil in the guise of promoting the good.
It is important for any conception of evil to distinguish it from merely bad or immoral acts. Evil acts are always immoral, trivially, but not all immoral acts are evil. It is not ipso facto evil to break promises or steal or tell lies or defraud or assault. In certain circumstances all these can be evil, but they are not evil in all circumstances. So we had better hope that they don’t turn out to be evil according to our definition. Nor do they: breaking a promise or stealing things are not intentional under the description “destroying the good”. They are not even cases of intending to do harm, even if they do in fact do harm. When I break a promise to you I have not identified a good in you that I proceed intentionally to eliminate; I simply act selfishly or lazily. Nor is it my aim in stealing from you to remove a good from your life; it is simply to add a good to my life. I would be quite happy to enhance my life by leaving yours undisturbed, so long as I get what I want; taking your things is just my means to enhancing my life. It is entirely contingent that my gain is your loss.
By contrast, if I decided to steal from you in order to deprive you of something precious to you, even if it meant nothing to me, then I would be acting evilly. But ordinary instrumental theft, in which I am merely trying to accumulate more goods for myself, does not exemplify the evil schema; I am not so much destroying a good as transferring it from you to me. Even assaulting another person, say in the course of robbery, is not evil by the criterion laid down here, since this is merely a means for me to get what I want. I am not trying to obliterate a good that you have; I am simply using the means necessary to my obtaining a good that I want. I would be quite happy to get what I want without assaulting you, but as it happens I have to. If I assault you intending to destroy your happiness and future, then I am acting evilly; but not all assault is so motivated. A crime it may be, and it is certainly immoral; but it is not evil, intuitively or according to our theory. It all depends on the motive behind the assault.
This is why, if the assault is disproportionate to the intended theft, it veers into the realm of the evil. If all I need to do is twist your arm, but I hit you on the head with a brick, then I have acted evilly, because I have removed more good from you than if I had used the minimal means to enact the theft. My action is immoral either way, but it is only evil when I destroy a good as an end in itself. Just war and self-defense both involve destroying good things, notably lives, but they are not evil because there is no intention to destroy the good as an end, just as a (proportionate) means. I would even distinguish between very bad acts and the subclass of bad acts I am calling evil acts. It is very bad to steal from helpless old ladies, and more so to assault them, but this is not a case of downright evil, as when you decide to terrorize old ladies for its own sake. It is when you take aim at their wellbeing itself that you become evil. The hardened criminal is not necessarily opposed to the good of others; he is merely out for his own good, irrespective of the deprivations he brings to others. But Iago is not just a self-centered criminal using Othello for his own enrichment; his intention is rather to destroy Othello, mind and body, without regard for how he might benefit. A career criminal would find Iago irrational, given the risks and potential payoffs, but Iago is quite rational given his real aims. He is in the business of removing the good not in acquiring goods.
The evildoer is therefore often quite difficult to distinguish from the mere criminal or immoralist. The actions look the same from the outside; it is the inner attitude that makes the difference. The same act of violence can be motivated by evil intentions or by merely criminal intentions. It would be easier if all evil actions were purely evil, i.e. motivated by nothing more than a desire to destroy something good. But some evil is instrumental—the agent expects to get something out of it himself. Here is where evil can shade into mere criminality or wrongdoing. Suppose I have a selfish aim and I am not too particular about how I achieve my aim: then I am not ipso facto evil, just rather unscrupulous. I might cheat people or coerce them or rob them to get what I want. This is not yet to act evilly towards others, because my focus is not destroying what is good for them. It is said by historians that the Germans at the beginning of their persecution of the Jews sought only to have them leave Germany: they made life difficult for Jews in the hope that they would voluntarily leave the country. These were no doubt deplorable and vicious policies, but they do not compare to the policies that succeeded them. If the Jews were not willing to leave voluntarily, then they would have to be exterminated. At first this was achieved by mass executions conducted wherever Jews lived, using bullets, but that was deemed inefficient, so special extermination camps were set up, where starvation and gas were used to kill people. Here the intentions of the Germans were nakedly sadistic and designed to bring about extreme degradation. They wanted to remove as much as possible of what makes life good from the Jews in their captivity. In this they entered the realm of evil quite decisively. They began to make the destruction of soul and body an end in itself. At the beginning they had an instrumental desire to force Jews into exile, but as time went on this was replaced by a desire to annul everything Jewish. They went from the merely criminal and bad to outright evil and depravity. They sought systematically and ruthlessly to destroy the good as exemplified in a population of people.
We find evil shocking in a way we don’t find routine crime shocking. Why? The theory gives us the answer: because the evil will is aimed at the destruction of the good. The criminal will is not: it is aimed rather at the good of the criminal, with indifference towards the good of others. But the evil agent is bent on the destruction of the good as such—in the purest case, he wishes simply to destroy what is good without any benefit accruing to himself. This is shocking, because we normally think that the pursuit of good states of affairs is what human motivation is all about. The evil agent inverts that assumption and aims to annihilate the good, not create it (in himself or others). We wonder why anyone would do anything so negative; hence the evil agent strikes us as a monster, a freak, even a paradox. The merely self-interested criminal, by contrast, is normal in his motivation, just unscrupulous. We wonder what the point of evil is, if it is aimed solely at the reduction of the amount of good in the world. No one’s utilities are being maximized. This raises the question of motivation, which I don’t want to get into here. Suffice it to say that envy, competition, and Schadenfreude often play a role. There is also, apparently, a brute appetite for destruction for its own sake—a kind of generalized vandalism. It may have to do with assertions of power, and certainly evil shadows power. In any case it is the opposite of the normal desire to bring about the good. 
Let me end with the question of natural evil, i.e. the kind that arises in the world independently of anyone’s will—earthquakes, floods, fires, disease, etc. This appears to be a counterexample to the theory defended here, since the natural destruction of the good is not an intentional destruction. Of course, if there is an agency behind it (say, Satan), then it fits our definition—these events are instances of intentional action. But suppose they are purely natural—what should we say about this kind of evil? My answer is that this is not a kind of evil; it is simply the occurrence of bad states of affairs. Talk of evil here is just a holdover from antiquated ways of thinking about the natural world, as if everything that happens must be willed by somebody. There are evil agents, but there aren’t evil facts or events or conditions. So the notion of “natural evil” is an oxymoron, unless we explicitly postulate an agent behind the bad events. A child dying of cancer is no doubt a horrible thing, but it is not an evil thing. What is called “the problem of evil” only arises when we introduce an agent like God. The problem is usually posed by asking why God allows horrible things to happen, as if he is a passive bystander too lazy or indifferent to lift a finger; and indeed, that is a form of evil (“passive onlooker evil”). Then evil is involved, but only because of an assumed agent—not because of the horrible event in itself.
But there is also the problem of active divine evil if we suppose that God is responsible for everything that happens—if he is the cause of all natural events. Then it looks as if God is actively, intentionally, and knowingly producing very bad states of affairs—that is, he is destroying the good on a grand scale. He then appears as an evil agent. This problem of evil (“active agent evil”) is even worse than the kind in which God is conceived as a mere onlooker, since it is his will that actively creates the bad state of affairs. How can God be good and yet he intentionally produces very bad states of affairs? The only conceivable answer relies on the model of the benevolent dentist, but that rings very hollow to most people. In any case, there is no counterexample here to the definition, since God would be evil if he intentionally destroys the good (without some excusing instrumental explanation). In either case (God or no God) the existence of “natural evil” poses no problem for our theory.
I hope that the theory I have presented strikes the reader as natural and intuitive, almost a truism. Truism or not, it still serves to bring order to our thinking about evil, by providing an account that discerns uniformity in the many varieties of evil. We don’t have to fall back on a disjunctive analysis or a vague family resemblance story, i.e. no definition at all. We now know what to look for when we are keeping our eye open for evil. Thus a theoretical advance might lead to a practical advance: we might become better at detecting evil, and hence preventing it. It is also good to reserve a special label for one particular kind of human badness, and we need to be able to justify the use of the concept of evil in our classifications of human actions. We need to know that the word “evil” denotes a coherent and well-defined natural kind—a distinctive moral natural kind. My view is that the concept of evil is a vital part of our moral conceptual scheme, corresponding to a very real type of human act. My aim has been to buttress the concept by providing a clear and straightforward definition of it, applicable to the major kinds of evil that exist. Absolute precision may not be possible, and borderline cases can no doubt be constructed, but I hope to have shown that the concept of evil deserves a place in our repertoire of moral concepts. Actually getting rid of evil may not be so easy.