Cambridge has taught me that general knowledge is a lie. It is often assumed that knowledge, especially at Cambridge, exists as a kind of constituted normative state. There is an unspoken baseline, a sense that there are certain things every intelligent person simply needs to know. The reality of ‘common knowledge’, though, is that it is often acquired through memory and perception rather than logic. What feels self-evident is not necessarily grounded in reason; it is grounded in familiarity.

I often link my thinking to the fact that I grew up in a relatively uncommon way. I am what some call a ‘third culture kid’ – someone raised outside both their parents’ native culture and their birthplace for most of their formative years. In my case, navigating my Latin American heritage alongside being born in the US, living in the Middle East, and then moving to the UK. This unconventional upbringing revealed that what one culture assumes is common sense is another culture’s niche trivia.

“Customs and beliefs around food, expression, language, and religion influence how we define normality”

This is not groundbreaking. But it becomes exaggerated in the Cambridge bubble, where ‘common knowledge’ no longer serves as a baseline of intelligence. Instead, it works as a social gatekeeper. It reinforces hierarchy and cliques more than we might like to admit. It becomes a collection of hyper-local, Western-centric norms that differentiate ‘insiders’ from ‘outsiders’: what you listened to at the dinner table, the sports, theatre, music or films you grew up with, the kind of friend group and family structure you had. All of these shape what you see as normative and quietly construct a sense of default knowledge.

Customs and beliefs around food, expression, language, and religion influence how we define normality. Moving around so much as a child leaves you slightly in-between and able to normalise various customs at once. For me, it was normal to hear the Adhan five times a day – in the middle of the night, at netball practice, while sitting my GCSEs. It was common knowledge among my largely international friend group when and why it played. In my Colombian household, headed by two literature professors, conversations about conflict, drugs, dictatorship and Gabriel García Márquez were also assumed common knowledge. Moving to the UK alone at sixteen meant navigating bureaucracy became common sense: managing my own finances, applying for visas, and navigating the NHS independently. Those were baseline skills in my context.

“The illusion that everyone knows what you are referring to – the punchline of your joke, the exact Financial Times article you mentioned – depends on constant reinforcement”

In other contexts, something else is assumed. When sarcasm is employed, it is treated as common knowledge that everyone will understand it is a joke. Knowing about the Premier League, having done Latin at school, being able to read inscriptions off monuments, pinpointing the Lake District on a map, identifying British accents. Pop culture references, films, music, slang words – these vary depending on where and with whom you grew up. Even navigating prestige hierarchies – firms, newspapers, jobs – or knowing how to network at an event and apply for your next internship. Other crucial things – like talking openly about emotions, politics, or money – are culturally shaped.

The point is not that these things are trivial, but that there is no such thing as ‘common knowledge’ – only knowledge so culturally dominant within a particular social sphere that we forget it is cultural at all.

What is even more interesting is how fragile ‘common knowledge’ actually is. Even within circles that appear culturally aligned, it collapses the moment doubt enters. It is not just ‘we both know X’. It is ‘we both know X, and we both know that we both know X’. If someone can plausibly say ‘I didn’t realise that’, the commonality disappears. If a politician makes a sexist joke and nobody objects, it becomes unclear whether anyone else found it offensive; without visible reaction, shared awareness dissolves. There may be shared understanding, but silence breaks coordination. The illusion that everyone knows what you are referring to – the punchline of your joke, the exact Financial Times article you mentioned – depends on constant reinforcement.

In the digital age, this becomes more complicated. We are constantly connected to external information through search engines, AI, and social media, on top of the reading we do for our degrees. The boundary between internal and external knowledge blurs. The volume of information we consume – news, memes, opinions – can inflate our confidence in what we know. We have all sat in a supervision where our partner and supervisor discuss a seminal text, idea or film and you have no idea what they are talking about. Sometimes it is not about preparation; it is about shared cultural references. Maybe you have not read Aristotle, seen Guernica, or watched the specific historical drama everyone is critiquing. You simply have not been exposed to it, even if it has nothing to do with your essay or degree topic. In this way, ‘common knowledge’ also creates the assumption that others are consuming the same information, especially in elite and intellectual circles. Algorithms often trap us in echo chambers rather than broadening our perspective, reinforcing our existing sense of normativity – and thus our version of ‘common knowledge’.

It may be more accurate, then, to think of ‘common knowledge’ not as stable, but as a fragile form of public coordination within specific social and cultural groups. The moment we assume a universal context, we sideline the lived experiences of those who did not grow up within a particular Western frame. There is no universal script. There are only overlapping spheres of familiarity, and the ability of one sphere to declare itself ‘common’.