If you’re a straight woman looking for love in your thirties, you have to find a man whose light is on. That’s the theory posited by Miranda in Sex and the City, who explained her now-infamous thesis in an episode of season three: “It’s not fate, his light is on, that’s all”, she explains to Charlotte, who is convinced her relationship with Trey was written in the stars.

“Men are like cabs; when they’re available, their light goes on,” Miranda continues. “They wake up one day, and they decide they’re ready to settle down, have babies, whatever, then they turn their light on.” The idea is then that whoever that man happens to meet next will wind up becoming his wife.

It sounds simple, insulting even. Surely, commitment is built over time? Romantic love is more complicated than a silly metaphor! There is more to men than a light flicking on in their brains and marrying whoever they happen to meet next. Despite these valid criticisms, the theory has remained popular since the cult HBO series thrust it into the mainstream in the early Noughties, especially among single women in their thirties.

Last month, a Substack piece on the “taxi cab” theory went viral for claiming that Harry Styles’s alleged engagement to Zoe Kravitz proves its legitimacy. “What else is there for a boy from Cheshire to do, other than marry the next available person?” the writer, Adele Miner, posits.

“Timing is a part of compatibility,” says the LA-based influencer, Olivia Victoria, in a viral TikTok on the subject. “Women have a greater tendency to make themselves ready when they meet Mr Right, whether they were ready or not, whether they were looking or not. Whereas men might meet their dream girl, and they won’t make themselves ready because they just aren’t ready.”

The logic is that, faced with the limitations of biology, women don’t always have the luxury of boundless time if they want to find a partner to have children with. Hence why we’re more likely to make ourselves ready for the right person, whatever the time; a behaviour that also stems from a scarcity mindset: “Okay, I like this one, and I might not find a better one in time, so even though I’m not totally ready, I will make myself ready so as not to lose him.”

Whereas men operate differently. “Men can have children whenever, so they don’t have to settle down when they find a really wonderful person. They can wait until they feel ready and then pick up the next person who gets in their cab,” adds Olivia Victoria.

So, when do they know it is the right time to turn their light on? “I think there’s a feeling where you’ve maximised as much joy as possible from, say, going out, or being reckless, and then it kind of becomes boring,” says Ryan*, 41, who recently settled down with a partner after years of noncommittal dating. “You look around, and you see that you’ve completed it and your friends have moved forward, started lives, and now their joy comes from somewhere else.”

There’s a scene in the 2010 film Greenberg, where Ben Stiller’s character is surrounded by all these people having a night out, and it just suddenly clicks for him as he realises he’s too old to be chasing the night. This, Ryan says, is how it feels when a man turns his light on. “You just get tired of the chase with potential partners: the will they won’t theys; the do they like mes; the idea that someone may be better suited to you,” he explains.

You look around, and you see that you’ve completed it and your friends have moved forward, started lives, and now their joy comes from somewhere else

Ryan, 41

Dating and relationships coach, Mila Smith, has observed the trend among her male clients, too, with many of them having long resisted commitment before suddenly deciding they’re ready to get married and have children. “What many of them have in common is that they eventually reach a turning point after experiencing a few emotional ‘bumps’ along the way: hurt, heartbreak and rejection leading to loneliness,” she explains. “Suddenly, being cavalier about relationships no longer feels as appealing. It’s almost as if they change when they get a taste of their own medicine. So the desire for deeper emotional (not just physical) intimacy and a stable long-term partnership moves much higher up the priority list.”

This was what happened to one of Smith’s clients, Sam*, who was nearly 30 when he split up with his long-term girlfriend; she wanted to spend more time together, make plans for the future and properly define the relationship. He wasn’t there yet.

Then he started dating someone new. And within a few months, that person did to him exactly what Sam had done to his ex, keeping him at arm’s length, avoiding conversations about the future and eventually stopped seeing him altogether.

“He described it as a shock exacerbated by the sudden realisation of what his ex-girlfriend must have felt like,” says Smith. “It became a major turning point for him. And while his first impulse was to seek his ex’s forgiveness because he was consumed by guilt, that relationship couldn’t be repaired. So, the experience fundamentally changed how he viewed commitment, emotional intimacy, and he now genuinely wants to settle down. His light is definitely on.”

But perhaps we aren’t giving men enough credit or agency in all of this. It might seem sudden to those on the outside, but internally, that journey may have been a long and slow transition.

“I think there’s probably some truth in the theory, but I also think it oversimplifies men quite a lot,” says Dan Somers, CEO and Founder of MANUP?, the UK-based men’s mental health support charity. “Through MANUP? I’ve spoken to thousands of men over the years and, truthfully, most would actually love to settle down, get married and build something stable,” he adds. “The issue is that many men now feel disposable.”

Heterosexual relationship dynamics have shifted hugely thanks to social media, where humorous content about the disastrous modern dating landscape runs rampant, often putting the onus on flakey, commitment-phobic men. The virality of these memes – because they really do spread quickly – is creating an unhelpful narrative about dating that is becoming inescapable, whereby women are victims and men are villains.

“Men constantly see messaging that they should earn more, look better, communicate better, achieve more, or essentially become a ‘better man,’ says Somers. “At the same time, women are often publicly celebrated online for leaving relationships, ‘cutting dead wood’, or starting again. That creates a lot of pressure and uncertainty for men, especially around commitment, trust and whether relationships are actually built to last anymore.”

In the past, Somers himself says he would’ve identified as someone who was anti-marriage; this changed as he got older – and became a Christian. “It started to look less restrictive,” he says. “I started seeing marriage as something grounded and solid rather than something designed to trap you.”

In the end, perhaps it all really boils down to maturity: the older you get, the more appealing commitment becomes. And yes, for some men, that realisation can probably happen rather quickly. “It’s all part of growing up; some people just take longer to come to terms with that,” says Ryan, who believes the taxi cab theory is an inevitable fate for the majority of straight men: “Call it Peter Pan syndrome, but even Peter grows up eventually, if you’ve seen Hook.”

*Names have been changed