In 2012, The Sun newspaper reported that the British MP Andrew Mitchell, then a prominent member of the UK government, had called a group of police officers ‘fucking plebs’. According to that story, the police thought about arresting him, but decided against it. In the wake of ‘plebgate’ (as this incident has become known), several journalists pointed to a double standard: Mitchell managed to escape arrest, but among the rest of us, arrests for swearing at the police are far from unheard of. These arrests have happened under Section 5 of the Public Order Act. People arrested under Section 5 can be issued with a Fixed Penalty Notice, and convictions can result in a fine. Swearing, it seems, can be a big deal. But why?

The Cambridge University Press’s online dictionary defines swearing as ‘rude or offensive language that someone uses, especially when they are angry’. Thinking of swearing as ‘rude or offensive language’ is a good start, but it is too rough for our purposes. For one thing, ‘rude or offensive language’ need not involve swearing at all. I am rude or offensive when I tell you that your new baby is hideous, when I accept your thoughtful gift without thanks, or when I crack a tasteless joke about death after you reveal that you have a terminal illness. Some definitions of swearing get around this issue by specifying that swearing should involve taboo (ie forbidden) language – but even this is not specific enough. Taboo language includes not only the familiar, bog-standard swear words like that mentioned above, but also other sorts of words that are not my focus here.

A category of non-swearing taboo language is blasphemous expressions and words that are otherwise unspeakable for certain religious groups. Another category is slurs: words that deride entire groups of people, and that are often associated with hate speech. In slurring someone – for example, by calling them a faggot – you express contempt not only for the person you are addressing, but also for a wider group to which they may belong; in this case, homosexual men. By contrast, in yelling ‘Fuck you!’ at someone, you do not express contempt for anyone other than the person you are addressing. The dividing line between swears and slurs is not clear-cut (we view ‘cunt’ as a swear, but it is deemed by some to be so universally offensive to women that it might be appropriate to view it as a slur too). The line between swears and religious taboo language is similarly fuzzy; consider that we can swear using the word ‘damn’. However, there is enough of a contrast between swearing and these other categories to make it worth separating them when we consider the ethical issues.

I’ll focus here on the non-slurring, non-religious swear words that, in English and many other languages, often have a sexual or a lavatorial theme. So, what’s special about these words? What sets them apart from other areas of language?

A clue is provided by the second part of the dictionary definition quoted above: the qualification that people swear ‘especially when they are angry’. It’s not quite right to link swearing uniquely with anger, but it does have a special role in expressing and communicating emotion. The expressions ‘My car has been stolen’ and ‘For fuck’s sake, my fucking car’s been stolen!’ both assert the same thing, but the second also conveys a sense of anger, desperation, and annoyance, thanks to the inclusion of swearing. As the linguist Geoffrey Nunberg has remarked, ‘[s]wear words don’t describe your feelings; they manifest them’. It is this unique role in expressing emotion that separates swearing from other uses of language, including other types of taboo language.

This unique psychological role gives swearing a unique linguistic role, too. Suppose we overhear somebody exclaim ‘Fuck it!’ when he accidentally spills tea in his lap. We can’t grasp the meaning of this exclamation by reflecting on the literal meanings of the words, as we’d do if the speaker had said ‘Eat it!’ or ‘Wash it!’ Someone who says ‘Fuck it!’ after slopping tea in his lap is not expressing a desire to fuck something, nor is he instructing anyone else to fuck something. To understand this exclamation, we need to consider not what the speaker is referring to or talking about, but what he aims to indicate about his emotions. This makes swearing, in such circumstances, more like a scream than an utterance: just like a scream, it expresses emotion without being about anything.

Perhaps this explains why swear words often fail to function like other words. Steven Pinker argues that ‘fucking’ is not an adjective because, if it were, ‘Drown the fucking cat’ would be interchangeable with ‘Drown the cat which is fucking’, just as ‘Drown the lazy cat’ is interchangeable with ‘Drown the cat which is lazy’. Quang Phuc Dong – a sweary pseudonym of the late linguist James D. McCawley – thinks, for various reasons, that ‘Fuck you!’ is not an imperative (that is, a command) like ‘Wash the dishes!’ One reason is that, unlike other imperatives, ‘Fuck you!’ cannot be conjoined with other imperatives in a single sentence. We can say ‘Wash the dishes and sweep the floor!’, but not ‘Wash the dishes and fuck you!’ And Nunberg suggests that ‘fucking’ is not an adverb like ‘very’ or ‘extraordinarily’, because while you can say, ‘How brilliant was it? Very,’ and, ‘How brilliant was it? Extraordinarily,’ you can’t say, ‘How brilliant was it? Fucking.’

The philosopher Joel Feinberg remarked that swear words ‘acquire their strong expressive power in virtue of an almost paradoxical tension between powerful taboo and universal readiness to disobey’. And, indeed, both in the UK and in many other cultures, we do much to prevent, censor, and punish swearing. This is often done informally: perhaps the most effective way of regulating swearing is through our awareness of attitudes towards it. Knowing that we face disapproval from others if we swear in the wrong context is effective at ensuring that we watch our language. But there are formal efforts to police swearing, too: swearing can get you fired from your job, fined, censored, and even arrested. The taboo against swearing is, it seems, a pretty serious matter.

A clue as to why lies in swearing’s focus on taboo topics, and the fact that different cultures give different weight to different taboo themes; for example, in English, blasphemous forms of swearing are relatively rare, and those that do exist – like ‘damn’ and ‘God’ – are considered pretty mild these days. But elsewhere, blasphemy plays a much larger role. Perhaps the most striking example is Quebec French, in which the strongest swears are terms relating to Catholicism. These include tabernak (tabernacle), criss (Christ), baptême (baptism), calisse (chalice), and osti (host). Je m’en calisse is equivalent to the English ‘I don’t give a fuck’. These expressions are considered stronger than standard French swears like merde (shit). They can be amplified by combining them with each other and with standard swears, as in Mon tabernak j’vais te décalliser la yeule, calisse (roughly, ‘Motherfucker, I’m gonna fuck you up as fuck’), and Criss de calisse de tabernak d’osti de sacrament (untranslatable expression of anger).

Blasphemy plays a large role in swearing in many religious cultures including Italian, Romanian, Hungarian, and Spanish – but some highly secular cultures also find religious swearing offensive. Godverdomme (Goddamn) remains one of the strongest expressions in Dutch. Perkele (the name of a pagan deity, now equivalent in meaning to ‘the devil’), Saatana (Satan), Jumalauta (literally ‘God help’, but used in a similar way to the English ‘Goddamn’), and Helvetti (hell) are all common and powerful ways of swearing in Finnish. For fanden, For helvede, and For Satan (‘For the devil’s/hell’s/Satan’s sake’) are widely-used Danish expressions; similarly, fan (Satan), helvete (hell), and jävla (derived from djävul, meaning ‘devil’) are common Swedish expressions.

While swearing’s power derives from taboo-breaking, the fact that swears refer to taboo topics does not explain why swearing itself is taboo

Some swearing is characterised by taboos relating to hierarchy; specifically, expressions of disrespect for certain individuals, commonly the mother of the person insulted. Examples include the Croatian expressions Pička ti materina (‘Your mother’s cunt’) and Jebo ti pas mater (‘A dog fucked your mother’); the Filipino Putang-ina (‘Whore-mother’); the Romanian Futu-ți dumnezeii mă-tii (‘Fuck your mother’s gods’) and Futu morții mă-tii (‘Fuck your mother’s dead relatives’); the Spanish Me cago en la leche de tu madre (‘I shit in your mother’s milk’), Me cago en tu tia (‘I shit on your aunt’), and Putamadre (‘Whore-mother’); the Turkish Ananı sikeyim (‘I fuck your mother’); and the Mandarin 肏你祖宗十八代 (‘Fuck your ancestors to the 18th generation’). The expression ‘Son of a bitch’ has equivalents in many other languages including French (Fils de pute), German (Hurensohn), Italian (Figlio di troia), and Turkish (Orospu çocuğu); as does ‘Motherfucker’ (for example, Mutterficker in German and Figlio di puttana in Italian).

Hierarchy and ancestry-themed swearing is less common in English – the expressions ‘Motherfucker’ and ‘Son of a bitch’ excepted – but the practice has a lofty historical pedigree. The following mother-disparaging exchange appears in William Shakespeare’s Titus Andronicus:

Demetrius Villain, what hast thou done?

Aaron That which thou canst not undo.

Chiron Thou hast undone our mother.

Aaron Villain, I have done thy mother.

Japanese offers perhaps the most striking example of a hierarchy-themed insult. One of the most effective ways to offend somebody in Japan is to address them as てめ, which is not a swear but a very derogatory form of ‘you’.

While swearing’s power derives from taboo-breaking, the fact that swears refer to taboo topics does not explain why swearing itself is taboo. There are, after all, inoffensive ways to refer to sensitive topics: we can say ‘poo’ or ‘faeces’ instead of ‘shit’, ‘vagina’ instead of ‘cunt’, and so on. While lavatorial and sexual functions are taboo, not all ways of referring to them are indecent. We are still in need of an explanation of what makes ‘shit’ more offensive than ‘poo’.

Some have suggested that the sound that swear words make contributes to their offensiveness. Pinker notes that ‘imprecations tend to use sounds that are perceived as quick and harsh’, and Kate Warwick hypothesises that the peculiar offensiveness of ‘cunt’ results from a combination of its meaning and ‘the sound of the word and the physical satisfaction of lobbing this verbal hand grenade’. There is something plausible about this. Trying to express anger using a swear word full of gentle, soft sounds – like the words ‘whiffy’ and ‘slush’ – would be the verbal equivalent of angrily trying to slam a door fitted with a compressed air hinge. Even so, the sound of swear words cannot fully account for their offensiveness. Many inoffensive words also sound ‘quick and harsh’, and some have benign alternative meanings (consider ‘prick’ and ‘cock’), or sound identical to parts of inoffensive words (‘cunt’ sounds identical to the first syllable of ‘country’ – a fact not lost on either John Donne, who ‘sucked on country pleasures’, or the anonymous author of the rugby song A Soldier I Will Be).

In any case, focusing on swear words themselves will not enable us to explain fully why they are offensive, because the offensiveness of a given utterance of a swear word is relative to the social and historical context. Swearing at a graveside during a funeral is more likely to cause offence than swearing while in the crowd at a football match, and using ‘damn’ is less likely to cause offence today than it was several decades ago. We can’t account for such contextual variations in swearing’s offensiveness by looking solely to features of swearing that do not vary with context, such as what swear words refer to and how they sound. We must look beyond the words themselves, and consider the broader behavioural contexts in which they appear.

Once we do this, the explanation is easier to find. We do, after all, have all sorts of preferences about how people behave. Many of these preferences are enshrined in our morality; others are associated with etiquette. Etiquette dictates that we hold our fork in our left hand and our knife in our right, that we remove hats when entering churches, that we say ‘thank you’ when people are kind to us, and so on. Etiquette varies with culture and upbringing, and its conventions are applied more strictly in some settings than in others. The fact that we have developed preferences for certain types of behaviour over others, often for apparently no good reason, makes it unsurprising that we should have preferences for certain forms of linguistic behaviour. Swearing is a form of dispreferred linguistic behaviour.

How do we get from this to an explanation of why swearing is offensive? Well, once we have established preferences about behaviour, the capacity for certain behaviour to become offensive arises quite naturally. To illustrate this, consider the following scenario (based on an actual and recurring series of events). Suppose that you make a new friend named Rebecca, and you fall into the habit of addressing her as Rachel. After you have done this a couple of times, Rebecca politely points out that her name is Rebecca, not Rachel. If, after she has drawn your attention to this, you persist in calling her Rachel, she is likely to begin to feel annoyed, and she might repeat the request to call her Rebecca. If you ignore her request a second or third time, then – provided that she has no reason to believe you have failed to understand her requests, nor that you are incapable of easily complying with them – she is likely to eventually view your behaviour as offensive. What started out as merely a dispreferred (by Rebecca) way of speaking, then, becomes offensive.

How does this happen? Well, the first time you call Rebecca Rachel, Rebecca takes you to have made an innocent and regrettably common mistake, and she assumes you meant no harm. When you continue to call her Rachel even after she has reminded you of her name, she concludes that you are being unreasonably inconsiderate of her wishes. And when you persist in calling her Rachel even after she has pointed out several times that this is not her name, it is difficult for her to avoid the conclusion that you are deliberately using an inappropriate form of address in order to upset her. Having started out assuming that you meant no harm, she comes to view your attitude towards her as hostile. And, indeed, it is hard to see how she could be mistaken.

In this example, we do not find an explanation for the offensiveness of the dispreferred expression in the expression itself. There is nothing whatsoever that is offensive about the name Rachel. Rather, the expression grows to be offensive after it has filtered through a chain of inferences that speaker and audience make about each other and about each other’s inferences. In essence: you know that Rebecca’s name is not Rachel, and you know that she dislikes being called Rachel, yet you nevertheless continue to call her Rachel; Rebecca knows that you know all this, and concludes from your behaviour in light of this knowledge that you are hostile towards her; you, in turn, recognise all this yet persist in calling her Rachel; Rebecca sees that you do this and so takes offence. Let’s call this way in which the offensiveness of dispreferred behaviour arises from these sorts of inferences between speaker and audience offence escalation.

Offence escalation promises to explain how swearing came to be viewed as offensive. The story begins with certain forms of speech being dispreferred. Once these preferences are established within a community of speakers, people’s knowledge that some expressions are to be avoided inevitably leads them to infer that if they do use a dispreferred expression, they will likely cause discomfort in their listener. And this makes using the dispreferred expression an even greater transgression: it is one thing unwittingly to use a disliked expression; quite another to use a disliked expression knowing that it is disliked, especially if our audience knows that we know that the expression is disliked. In the latter case, but not necessarily in the former, our audience has good reason to doubt our goodwill towards them; consequently, they are offended.

We need to add something to this offence escalation story to explain how words become swear words. As I have outlined it, offence escalation enables any word to become offensive, at least to someone, provided that it involves a word that the listener dislikes. As we see from the Rebecca/Rachel example, even a perfectly respectable name can become offensive to someone when used in a certain way. However, swear words are not merely words that are disliked, and which have subsequently grown to be offensive through a process of offence escalation. After all, ‘Rachel’ is not a swear word, even when used as described above. In addition to being dispreferred, swear words also share certain features in common, such as their focus on taboo topics like sex and defecation. They also, as we have noted, sound a certain way. Offence escalation does not explain why it is the taboo words with a particular sound, rather than other sorts of words, that get to be swear words.

The ‘quick and harsh’ sound of swear words plausibly adds drama to the gleeful thrill of taboo-breaking

In fact, that swear words are taboo-focused fits neatly into the offence escalation story. For a speaker to get the offence escalation process started, she needs to use an expression that she knows her listener will dislike. How can she do this? Well, if she knows her listener well enough to have a good sense of what sort of utterances he will dislike, then her job is easy, and she is well on her way to being able to offend him. For example, if her listener is sensitive about losing his hair, she can call him ‘baldy’. But what if the speaker knows nothing about the listener’s preferences? Or, what if the speaker is addressing multiple people with various preferences? Can she cause offence in these circumstances? The existence of taboos means that the answer is yes.

Provided that speaker and audience recognise the same taboos – which is likely if they belong to the same culture and speak the same language – the speaker knows something about which expressions her audience will probably dislike. She knows that her audience will likely find commonly dispreferred ways of referring to taboos unpleasant. And her audience will know that she knows that they will find such references unpleasant. This enables the offence escalation process to get off the ground. Moreover, it enables it to occur on a much larger scale, and much faster, than in the Rebecca/Rachel example described above: since taboo-related preferences are (and are known to be) widespread within a culture, one can annoy a great many people at once with a single taboo reference. And, unlike in the Rebecca/Rachel case, one’s audience does not need to point out that a given (taboo) expression is inappropriate, since everyone will take the speaker to understand this already.

The existence of widely recognised taboos, then, offers a fast-track route for certain expressions to become widely offensive. It also provides a certain motivation for this to happen: breaking widely recognised taboos can (unlike calling people by the wrong name) be thrilling. Shocking people can sometimes be fun. Perhaps this helps explain why swear words tend to sound a certain way: the ‘quick and harsh’ sound of swear words may not alone be enough to account for their offensiveness, but it plausibly adds drama to the gleeful thrill of taboo-breaking, so it should not be surprising that it is the fierce-sounding references to taboos that are singled out to become swear words.

However, swear words are more than words that are universally offensive within a given culture. Slurs, too, fit this description. It seems plausible that slurs, like swears, grow to be offensive through a process of offence escalation, yet they differ from swears in that they express contempt of a given group. Why is it that some widely dispreferred words develop into swear words whilst others develop into slurs?

I think that the answer lies in what the use of the dispreferred words is taken by speaker and audience to convey. That ‘fuck’ grows to be an offensive swear word can be attributed to the fact that the fuck-exclaiming speaker’s audience takes the speaker to be inconsiderate of their dislike of the word. That ‘nigger’ grows to be an offensive slur can be attributed to something a little different: to the audience’s recognition that the speaker aims, through the use of this dispreferred word, to convey her contempt of black people. We might also add – as philosophers who write about slurs sometimes do – that by using a slur, a speaker attempts to make her audience complicit in her contempt, by signalling that she believes herself to be among people who share her contempt. This, too, is offensive to an audience who does not share this contempt, and is insulted to be taken to do so. We can view the process of offence escalation as similar in the case of both swears and slurs – both involve the speaker’s and audience’s shared knowledge that the word is dispreferred – but whereas in the case of swears, the offence arises merely from the knowledge that the word is dispreferred (and therefore the speaker is inconsiderate in choosing to use it), in the case of slurs the offence arises also from the knowledge that the speaker aims to communicate to her audience a contemptuous attitude towards a certain group, and perhaps also an assumption that her audience shares this attitude.

Swearing, then, is as offensive as it is not because of some magic ingredient possessed by swear words but lacked by other words, but because when we swear, our audience knows that we do so in the knowledge that they will find it offensive. This is why context is important: there are some contexts in which we know we will not cause offence by swearing, and when we swear in such contexts our audience’s knowledge that we did so without expecting or intending to offend helps ensure that we do not offend. This explains why we are more tolerant of swearing by non-fluent speakers of our language, such as young children and non-native speakers, than we are of swearing by competent speakers. When non-fluent speakers swear, often we do not suspect them of doing so knowing that their words are offensive. Consequently, we are less likely to be offended.

You would find my refusal to thank you for your good turn rude, but you would probably not deem it morally suspect

Offence escalation helps explain why some swear words are more offensive than others; for example, why ‘cunt’ is more offensive than ‘shit’. Initially, ‘cunt’ is more strongly disliked than ‘shit’. Anyone who realises this, and who is taken by their audience to realise this, commits a greater transgression by saying ‘cunt’ than by saying ‘shit’. And that we know that we commit a greater transgression by saying ‘cunt’ than by saying ‘shit’ itself magnifies the offensiveness of ‘cunt’ relative to ‘shit’. The stronger the norms against using a particular expression, the greater the offensiveness of using that expression. In turn, the greater the offensiveness of a particular expression, the stronger the norms are against using that expression. Swearing’s offensiveness feeds itself.

What does this tell us about whether or not swearing is morally wrong? It is helpful, once again, to compare swearing to etiquette breaches. Since it’s preferable not to upset people where we can easily avoid doing so, we have some reason not to swear in contexts where it is likely to offend. The same holds for etiquette breaches. Even so, in most cases, we tend not to view breaches of etiquette as immoral, even where it causes offence. You would find my refusal to thank you for your good turn rude, but you would probably not deem it morally suspect. You would make a similar judgment were I to swear in the course of a polite conversation.

This is not to say that swearing, or breaching etiquette in some other way, is never immoral. We can imagine situations where breaching etiquette – by swearing inappropriately, addressing someone in an over-familiar way, refusing to adhere to a dress code, failing to say ‘please’ and ‘thank you’, and so on – would cause upset, and we can imagine situations where we might deem it morally wrong. Such situations might involve breaching etiquette with the intention to belittle, distress, harass, intimidate, provoke, and so on. But most cases of etiquette breach – including most cases of swearing – are not like this. With this in mind, some of our efforts to punish and prevent swearing – such as arrest under the Public Order Act – seem overly draconian. Swearing is often objectionable, but rarely immoral.