Right now, you’re sitting on information to which only you have access. Not all of it is secret. Apart from you, no one knew whether you were going to look at this website, and if they had, well - so what. But if the wrong person found out about the earnings you haven’t declared, your plans to quit your job, or your adulterous fantasies, you’d be in trouble.

It’s this potential danger that defines the secret, and it’s what distinguishes it from an enigma. Unlike a secret, which stops being secret the moment it comes to light, an enigma remains enigmatic no matter how many people know about it. Think of the Mona Lisa - she couldn’t be more on display, more exposed, more reproduced, or more recognised, but the mysteriousness of her smile persists. There’s nothing secret about her, but she’s highly enigmatic; instantly familiar, yet enduringly strange. So if you feel any anxiety in keeping the secrets you keep, it’s because, unlike enigmas, secrets are not safe, are not in themselves cryptic - to be understood, they need only be let out.

What if the secret’s not yours? What if a friend confesses to an affair? He gets you to swear to tell no one. But now two people know, and that raises the question of how many more could he tell, and it still be a secret. Five? How many knew in advance about 9/11? For an operation of that scale, you’d guess at least 50... There’s probably only 50 people who know the history of Norwegian punctuation, but do they have a secret? No, a secret must be dangerous, regardless of how widely it’s kept - like the networks of the French Resistance. And your friend’s infidelity is catastrophic.

But as he lets you into his secret, ironically, he makes himself an enigma. His disclosure causes you to wonder how well you knew him; you marvel at this stranger inside your friend. The secret comes out, but its author gets darker, and there’s an alienation effect.

Unlike enigmas, secrets revealed become ordinary; but those who reveal them become enigmatic.