Finding form-context-fit is like solving a Sudoku. To figure out which number should go into a square, you look at the other numbers in the same row—it can’t be one of those numbers; that’s one constraint. Then you look at the numbers in the same box; it can’t be one of those either. Once you’ve figured out all the numbers that are not allowed, you

a design is good if and only if the form (of the solution) fits the context (of the problem).

It was in Notes in 1964 that Alexander introduced his now-famous idea of form-context-fit. These days, I mostly see it referenced in the phrase product-market-fit —meaning you’ve found a product that consumers are hungry to pay for—but it was originally a broader, deeper, and more interesting idea.

When faced with a difficult problem, don’t try to solve it. Instead, make sure you understand it. If you understand it properly, the solution will be obvious.