Fermat was not interested in writing a textbook for future generations: He merely wanted to satisfy himself that he had solved a problem. While studying Diophantus’s problems and solutions, he would be inspired to think of and tackle other related and more subtle questions. Fermat would scribble down whatever was necessary to convince himself that he could see the solution and then he would not bother to write down the remainder of the proof. More often than not he would consign his inspirational jottings to the bin, and then move on to the next problem.
