Plot the good-and-bad fortune of a story against its page number and the line has a shape — and there are only about six of them. Vonnegut drew them on a chalkboard; a machine later confirmed them in thousands of books. Slide through the arcs (or tap).
The six emotional arcs of stories (Reagan, Mitchell, Kiley, Danforth & Dodds, 2016 — a singular-value decomposition of sentiment in 1,300+ novels recovered essentially six dominant shapes). RAGS TO RICHES (a steady rise) · TRAGEDY / RICHES TO RAGS (a steady fall) · MAN IN A HOLE (fall then rise) · ICARUS (rise then fall) · CINDERELLA (rise-fall-rise) · OEDIPUS (fall-rise-fall). Each is drawn as its sentiment(time) curve; the number of turning points — 0, 0, 1, 1, 2, 2 — is what distinguishes them. A fail-loud self-check throws unless the rise is monotone up, the fall monotone down, and the turning-point counts match.
Idealised smooth curves stand for the SVD modes (real arcs are noisy and blend); sentiment analysis is itself approximate. The turning-point structure and the endpoints shown are exact for these curves.