A single marginal note created a 350-year mathematical obsession

Around 1637, Pierre de Fermat wrote in the margin of a copy of an ancient mathematics text that he had discovered a proof that no three positive integers could satisfy a certain equation for any power greater than two, adding that the margin was too small to contain the proof. He never wrote it down elsewhere, and the claim sat essentially unresolved for over three centuries after his death.

Singh treats this as the ultimate mathematical taunt: a deceptively simple statement, easily understood by a beginner, claimed proven by a serious mathematician, with the actual proof permanently missing. The apparent simplicity of the claim, contrasted with mathematicians' repeated failure to reconstruct any proof, made it uniquely tantalizing across generations, since something this easy to state seemed like it should have an accessible solution.

The mystery of whether Fermat genuinely had a valid proof, or was mistaken, remained open the entire time, adding a layer of historical intrigue to what was already a purely mathematical puzzle.

Takeaway: simplicity of a claim says nothing about the difficulty of proving it — the gap between the two can span centuries.