The Great Debate

Forty+ years later, the controversy surrounding the Appel and Haken proof is amazingly alive and well. Even when the extraordinary in many respects Appel and Haken’s proof was just announced, the President of the Mathematical Association of America Lynn Arthur Steen was very careful [Ste]: he did not write that the conjecture had been proved but instead used the word “verified” in describing the most important mathematical event of that year.