If Instagram is to be believed, our authentic self should be in an Alpine snowscape somewhere in chunky knitwear, laughing photogenically over an artisanal brunch. Search the site for the hugely popular hashtag #authenticity and you will be reassured that apparently nobody’s authentic self is fat, or spotty, or poor or has run out of milk and can’t be bothered to go to Tesco.

This is authenticity as lifestyle choice – a kind of “hygge meets Oprah”. It is also, by any measure, an irony, given that these “authentic” pictures often take hours to create. The more preening and curated our lives have become online, the more we claim to value the real over the ersatz.

In recent years, many of us have become fixated on the idea of authenticity in everything from people to pasta sauce. The middle classes compete over the most authentic brand of olive oil or southeast Asian beach or organic chicken farm. Donald Trump rose to power on brand authenticity – promising a new kind of unfiltered, teleprompter-free politics, ditching formal press briefings in favour of smearing his naked id all over Twitter. “Be true to yourself” is one of the most common pieces of advice given in American graduation speeches. But does this core authentic self living inside each of us actually exist? And if it does, is he or she someone we would want to meet?

Philosophers debate the point, but it seems likely that instead of possessing one fixed, essential self, we are all just a messy, shapeshifting collection of traits and tendencies that wax and wane over time. These various “selves” – both good and bad, noble and selfish, jostle for prominence from moment to moment.

But even assuming, for the sake of argument, that we do each have a core authentic self, it is a strange vanity to think that it is this deeper, unfiltered version of ourselves, as opposed to the more restrained one, that we show to the world, that is the good guy – the better part of our nature.

My own authentic self, sadly, is a fan of pyjamas and inertia. She doesn’t take out the bin or write thank you notes, or file tax returns. Her heart tends to sink when she spies the lonely man from next door and knows that she is in for a detailed briefing about the last residents’ association meeting. It is only a stern intervention from my more manufactured, inauthentic self that stops this authentically antisocial monster from shouting: “FOR THE LOVE OF GOD DON’T TALK TO ME!” and running in the opposite direction.

Authenticity is, at heart, the idea that we should make the way we behave on the outside match what we feel on the inside. But really, a functioning society depends on keeping a healthy distance between the two.

Staying “true to yourself” can too easily become “prioritising my own feelings and needs above everyone else’s”. But to live a civilised and connected life we should really be constantly second-guessing and checking our “authentic selves”, addressing our biases, biting our tongues and filtering what we say for hurtfulness or idiocy, saddling up occasionally and doing the difficult but kind thing.

This is, of course, not an argument that anyone should be living a fundamental lie about any important aspect of his or her life or beliefs. But as a rule, inauthenticity is underrated. No need to seek out your authentic self. You can do better than that.

Ruth Whippman is the author of The Pursuit of Happiness: Why Are We Driving Ourselves Crazy and How Can We Stop? (Random House, £9.99). To order a copy for £8.49, go to bookshop.theguardian.com