Why is breaking a mirror seven years of bad luck?

The idea traces to a Roman belief that a reflection held part of the soul, so shattering a mirror was thought to harm the person reflected. It was reinforced by the fact that mirrors were once expensive, making a break a genuine loss. The seven years came from an old notion that the body renews itself over roughly that span, after which the harm would pass.

Why is it bad luck to walk under a ladder?

A ladder leaning against a wall forms a triangle, a shape long read as sacred and not to be broken by passing through it. A darker strand links ladders to the gallows, where they were used in hangings, giving them an association with death. Both are old symbolic ideas rather than any real danger, though there is also the plain practicality of not walking beneath someone working above.

Why do people throw salt over their left shoulder?

Salt was once precious and hard to obtain, so spilling it was treated as a real misfortune. Throwing a pinch over the left shoulder was meant to strike or blind the devil, who was imagined lurking behind you, since the left side was traditionally associated with evil. It is a ritual of warding rather than anything with an effect on events.

Are black cats good luck or bad luck?

It depends entirely on where you are. In parts of Europe and North America a black cat crossing your path is read as bad luck, tied to old associations with witches, while in Britain and other traditions a black cat is a sign of good fortune. The fact that the meaning reverses by culture shows these are inherited stories rather than any real property of the animal.

Common superstitions explained: where they really come from

Broken mirrors, spilt salt, black cats and knocking on wood — the surprisingly logical histories behind the habits we half-believe.

6 min read · Published 28 August 2026

The short answer

Most everyday Western superstitions have traceable origins in old beliefs and practical history rather than in any real power. A broken mirror meant seven years' bad luck because Romans thought a reflection held part of the soul and because glass was once precious; walking under a ladder was avoided for the sacred triangle it forms and its link to the gallows; spilt salt was serious because salt was valuable, and a pinch thrown over the left shoulder was aimed at the devil imagined behind you. Black cats, knocking on wood, umbrellas opened indoors and magpies all carry similar inherited stories. They are habits passed down, not mechanisms that shape events.

Superstitions are history in disguise

Most of us keep a few superstitions we would never quite defend — a small knock on the table, a reluctance to walk under a ladder, a wince when a mirror cracks. What makes them fascinating is that almost every one has a real history behind it. They are not random; they are old ideas and old practicalities, worn smooth by centuries of repetition until only the habit remains and the reason is forgotten.

Recover the reason and the superstition suddenly makes a kind of sense. Salt was precious. Mirrors were expensive. Trees were thought to hold spirits. What survives as "bad luck" is very often a memory of something that once mattered for an ordinary reason. Here are the origins behind the most familiar ones.

The origins, one by one

Each of these is a case of a practical fact or an old belief hardening into a rule. The table pairs the superstition with its likeliest origin.

Superstition	Likely origin
A broken mirror means seven years' bad luck	The Roman idea that a reflection held part of the soul, so breaking it harmed you — and glass was once so costly that breaking a mirror really was a small disaster. Seven years came from an old notion of the body renewing over that span.
Don't walk under a ladder	A ladder against a wall makes a triangle, read as a sacred shape not to be broken. A grimmer strand ties ladders to the gallows, where they were used at hangings.
Spilling salt is bad luck	Salt was precious and hard-won, so wasting it was serious. Throwing a pinch over the left shoulder was aimed at the devil, imagined lurking at your back, to blind or ward him off.
A black cat crossing your path	Associated in parts of Europe with witches and ill omen, though in other places — and other eras — a black cat crossing your path was read as good luck, so the belief itself reverses by culture.
Knock on wood, or "touch wood"	Older ideas of protective spirits living in trees, touched for their help — or, more simply, a way to avoid jinxing a hope you have just spoken aloud.
Opening an umbrella indoors	Often tied to the awkward, genuinely hazardous business of opening a stiff, spoked umbrella in a cramped indoor space, later dressed up as an affront to the sun or house spirits.
One for sorrow (magpies)	From the old counting rhyme, where a single magpie is read as an omen of sorrow and two as joy — a habit of greeting a lone magpie survives in Britain and Ireland today.

Common Western superstitions and their likely origins. These are inherited habits, not mechanisms that act on events.

Read down the column and a pattern appears: nearly every "bad luck" is a fossil of something once sensible — a costly object, a real danger, an old faith in spirits or a wish not to tempt fate by naming a hope out loud.

Why the same act can mean opposite things

As with a twitching eye, some of these superstitions flatly reverse depending on where you are. The clearest is the black cat: an omen of bad luck in parts of Europe and North America, but a bringer of good fortune in Britain and in other traditions entirely. One animal, opposite meanings, decided purely by which culture's story you inherited.

This is the tell that we are dealing with folklore rather than fact. If black cats truly carried luck one way, the luck would not flip when you crossed a border. What flips is the story, and the story is local — much like the way unlucky numbers change from 13 in the West to 4 across East Asia.

Why we keep them anyway

Knowing the origin rarely cures the habit, and that is the interesting part. Plenty of people who would never claim a mirror can harm them still feel a flicker when one breaks, and still knock on wood after saying "touch wood, we've never had a problem." The superstition has outlived the belief.

That is because these little rituals do something quiet and useful. They give a shape to hope and anxiety — a small action to take when you want to protect a good thing or push back a worry you cannot otherwise touch. In that sense they sit close to the comfort people find in reading a coincidence as synchronicity: not a lever on the world, but a way of feeling less at its mercy.

So there is no need to be sniffy about them. Knock on wood if you like. Just hold it lightly, as an inherited habit with a good story behind it, rather than a mechanism that bends how the day will go.

Common questions

Why is breaking a mirror seven years of bad luck?: The idea traces to a Roman belief that a reflection held part of the soul, so shattering a mirror was thought to harm the person reflected. It was reinforced by the fact that mirrors were once expensive, making a break a genuine loss. The seven years came from an old notion that the body renews itself over roughly that span, after which the harm would pass.
Why is it bad luck to walk under a ladder?: A ladder leaning against a wall forms a triangle, a shape long read as sacred and not to be broken by passing through it. A darker strand links ladders to the gallows, where they were used in hangings, giving them an association with death. Both are old symbolic ideas rather than any real danger, though there is also the plain practicality of not walking beneath someone working above.
Why do people throw salt over their left shoulder?: Salt was once precious and hard to obtain, so spilling it was treated as a real misfortune. Throwing a pinch over the left shoulder was meant to strike or blind the devil, who was imagined lurking behind you, since the left side was traditionally associated with evil. It is a ritual of warding rather than anything with an effect on events.
Are black cats good luck or bad luck?: It depends entirely on where you are. In parts of Europe and North America a black cat crossing your path is read as bad luck, tied to old associations with witches, while in Britain and other traditions a black cat is a sign of good fortune. The fact that the meaning reverses by culture shows these are inherited stories rather than any real property of the animal.