In the 1960s, the French novelist Alain Robbe-Grillet became so frustrated by the manner in which his nouveau roman movement was framed and discussed in public that he devised a rule of thumb: whatever you hear or read about it, presume that the exact opposite is true. The same rule might be applied to recent British political events. A coup orchestrated and bankrolled by hedgefund managers, media tycoons and privately educated politicians is described, time and again, as an “anti-establishment uprising”. The proposed handing to offshore corporations of blank slates on which to write, from offices in Austin or Beijing, their own contractual and fiscal terms unfettered by EU tax and worker protection laws is presented as “taking back control”. And a phenomenon – immigration – that has been shown as a matter of factual record to add enough to the exchequer for a primary school or doctor’s surgery to be planted in every second neighbourhood up and down the country is painted, almost without contest (even by opposition frontbenchers) as a “strain” on public resources.

It doesn’t take a novelist’s eye to draw these paradoxes into focus. But amid the post-truth wildfire that has flared on both sides of the Atlantic, and which threatens to extend its flames later this year to continental Europe’s dry bracken, one particular instance of prestidigitative false-speak has struck me as an affront so grievous and fundamental that it clamours above all the others. In October last year, at the Conservative party conference, Theresa May famously goaded her opponents with the words: “If you believe you’re a citizen of the world, you’re a citizen of nowhere.” She went further, chastising them: “You don’t understand what the very word ‘citizenship’ means.” Now this one I feel moved to unpack. Not for the irony that she delivered these words as she planned to extra-judicially strip millions of the EU citizenship to which, since 1993, we’ve been (and still are) legally entitled; nor because they echoed (one hopes unintentionally) the Nazis’ rhetorical move of using the term “rootless cosmopolitan” to signal “Jew”. No, what spurs me to comment on May’s claim is the fact that, in making it, she invoked a decidedly literary concept.

Citizenship, despite the Home Office’s farcical attempts to rebrand it as a “British value”, is a notion that originates in Greece. You see it being moulded and honed in the comedies of Aristophanes, the tragedies of Euripides and Sophocles. Greek theatre was not simply a means of entertainment, nor even of representing society back to itself; rather, it provided the smithy in which the basic concepts that underpinned a state were forged in the first place – a quasi-sacred mechanism for placing order and meaning in the world.

Nowhere is this more apparent than in Aeschylus’s Oresteia. First performed in 458BC, the trilogy charts the move from tyranny to the creation of a divinely mandated but secularly managed form of early participatory democracy. After Agamemnon, king of Mycenae, is murdered by his wife Clytemnestra on his return from sacking Troy, their son Orestes kills her in revenge and is then pursued from place to place by hound-like Furies – goddesses of revenge – bent on exacting bloody retribution for his matricide. The cycle’s third and final play, The Eumenides, finds Orestes seeking sanctuary in Athens, clinging to a statue of the city’s deity Athena. Athena appears on stage in person and demands to know what’s up. Orestes confesses to his mother’s killing, but argues (in tandem with his advocate Apollo) that this act was justified, indeed required, by her treacherous slaying of Agamemnon. The Furies counter by pointing out that Clytemnestra was herself avenging Agamemnon’s sacrificing of their daughter Iphigenia (which he did in order to raise winds to bear his fleet to battle); and they contend that the killing of a mother is more heinous than that of a husband, since (unlike a married couple) mother and son are of the same flesh.

Citizenship, despite the Home Office’s farcical attempts to rebrand it as a 'British value', originates in Greece

Both positions have much to recommend them. Taken on their own terms, they’re each pretty sound. The genius of Aeschylus is to set these claims and counterclaims in dialogue with one another, in a way that calls for careful negotiation and transformative resolution. And the genius of Athena, goddess of wisdom, shines through in what she does next. Realising she has a complex situation on her hands, in which the stakes are high (she can’t risk alienating either her fellow god Apollo or the Furies, who threaten to desecrate her city’s fields and population if they’re slighted), she proposes something radical and unprecedented: 12 of her wisest citizens will hear both sides out, then come to a decision by each casting a vote. Whatever the outcome of this trial, she decrees, this custom shall hold sway from this day forth in Athens.

That Orestes is (by the skin of his teeth) acquitted is almost incidental. What matters, what persists in perpetuity is the political order that is generated by the episode: civic democracy. For Athens, this is not simply a static, inward-facing or self-contained order: the goodwill of Orestes, who leaves to assume power back home, guarantees peaceful trade and military solidarity between Athens and Argos. At the same time, to placate the Furies Athena grants them a permanent residence within the city, a grotto from which they, too, can issue protection to supplicants. Thus, in opening her city to not just one but two foreign bodies, and reconfiguring its practices and layout through this opening-up, Athena secures an age of prosperity that will place Athens at the very centre of the Hellenic universe.

Charting the move from tyranny to democracy … The Remorse of Orestes (1862) by William-Adolphe Bouguereau

Two vital points follow from this. Firstly, that democracy is structural. The legal mandate for Orestes’ verdict comes not from (for example) the Furies whipping up hatred of him among the general Athenian populace, even if they might have won over a majority by so doing. If civic justice worked like that, then William Golding’s Lord of the Flies would be taught in schools as a positive illustration of “people power”. Democracy takes place when civic institutions – brilliantly embodied by Golding’s conch shell – uphold due process, even when there are only 12 (or three) people on a particular panel. In this respect, Trump’s disparagement of a judge for being of Mexican heritage and May’s refusal to condemn newspapers that more or less openly incited violence against justices who ruled against her places these two firmly in the conch-smashers’ camp.

Secondly, that one is a citizen not simply because of an internal relation to one’s community, although that’s part of the picture, but because of a relation to a complex, often troubled outside; through the acceptance of the outsider into your place and yourself into theirs. As the philosopher Simon Critchley, discussing the Oresteia 10 years ago (appropriately enough, in Athens), put it: “A city, a polis, for us a nation-state … only is through a dialogical relation to the foreign and the foreigner.” It turns out that May is not just wrong; she’s exactly wrong. If you’re not a citizen of the world you’re not a citizen of anywhere. You’re not even a citizen; you’re just a subject.

It might not be realistic to expect our leaders to have read the Oresteia (indeed, it’s unlikely any future ones will have, since under this government classics A-level faces the chop). But it is incumbent on them to understand the concepts they’re invoking – all the more so at a time when, on both sides of the Atlantic, these concepts might turn out to name the fulcrum around which two conditions, two conjoined yet quite divergent futures, those of democracy and tyranny, hang in the balance.

• Citizens of Everywhere is a project by the Centre for New and International Writing at the University of Liverpool. @CitizensofWhere #CitizensofEverywhere Tom McCarthy’s most recent novel is Satin Island. The fee for this article will be donated to Hope not Hate.