A box of tacks
You are given a candle, a book of matches and a box of drawing pins. Fix the candle to a wall so it can burn without dripping wax on the floor. This is the candle problem, published by the psychologist Karl Duncker in 1945. Most people try to pin the candle directly or glue it with melted wax. The solution is to empty the box, pin it to the wall as a shelf, and stand the candle inside.
Duncker called the obstacle functional fixedness: the box was seen as a container for pins, not as a material. The constraint was never the box. It was the meaning assigned to it.
Where the term comes from
The Maltese physician Edward de Bono introduced "lateral thinking" in The Use of Lateral Thinking (1967). He contrasted it with vertical thinking, which digs deeper into one approach, and argued for deliberately provoking alternative ones. De Bono was not Nordic, and lateral thinking has no special regional origin. We include it because it describes, better than any other term, what good Nordic puzzles — and many others — ask of their solvers.
Games that change their own rules
Finnish developer Arvi Teikari's Baba Is You builds an entire game from this idea. Rules appear as word blocks on the level, such as WALL IS STOP. Push the words apart and walls no longer stop you. The puzzle is not the maze; it is the sentence that defines the maze.
Piet Hein's Hex offers a quieter lesson. Because the board cannot end in a draw, John Nash later showed that the first player must have a winning strategy, even though nobody can easily say what it is. Knowing a solution exists changes how players approach the board.
Three ways to step sideways
- Restate the goal in other words. "Fix the candle" becomes "make a surface at candle height".
- List what each object could be. A box is also a shelf, a wall, a lever, a mould.
- Remove a rule on purpose. Ask what you would do if one constraint vanished, then see whether it was ever real.
Practise the move
Six matches lie on a table. Make four equilateral triangles of equal size, each side one match long. No breaking or bending.
On a flat surface it cannot be done. Lift three matches to meet above a triangle of the other three: a tetrahedron. Four faces, four triangles.
Nothing said the answer had to be flat. The table supplied the assumption. Where in your work does the surface you happen to be working on define the shape of the answer?
Reflection prompts
When did you first feel stuck?
Note the moment. Stuckness usually coincides with an assumption hardening into a rule.
Which assumption did you drop?
Name it in a sentence. Writing it down makes it easier to recognise next time.
Would the solution survive a new constraint?
Add a rule back — no lifting, no stacking — and see what alternatives appear. Lateral thinking works in both directions.